Byte vs column awareness for diagnostic-show-locus.c (PR 49973)

contrib/ChangeLog

2019-12-09  Lewis Hyatt  <lhyatt@gmail.com>

	PR preprocessor/49973
	* unicode/from_glibc/unicode_utils.py: Support script from
	glibc (commit 464cd3) to extract character widths from Unicode data
	files.
	* unicode/from_glibc/utf8_gen.py: Likewise.
	* unicode/UnicodeData.txt: Unicode v. 12.1.0 data file.
	* unicode/EastAsianWidth.txt: Likewise.
	* unicode/PropList.txt: Likewise.
	* unicode/gen_wcwidth.py: New utility to generate
	libcpp/generated_cpp_wcwidth.h with help from the glibc support
	scripts and the Unicode data files.
	* unicode/unicode-license.txt: Added.
	* unicode/README: New explanatory file.

libcpp/ChangeLog

2019-12-09  Lewis Hyatt  <lhyatt@gmail.com>

	PR preprocessor/49973
	* generated_cpp_wcwidth.h: New file generated by
	../contrib/unicode/gen_wcwidth.py, supports new cpp_wcwidth function.
	* charset.c (compute_next_display_width): New function to help
	implement display columns.
	(cpp_byte_column_to_display_column): Likewise.
	(cpp_display_column_to_byte_column): Likewise.
	(cpp_wcwidth): Likewise.
	* include/cpplib.h (cpp_byte_column_to_display_column): Declare.
	(cpp_display_column_to_byte_column): Declare.
	(cpp_wcwidth): Declare.
	(cpp_display_width): New function.

gcc/ChangeLog

2019-12-09  Lewis Hyatt  <lhyatt@gmail.com>

	PR preprocessor/49973
	* input.c (location_compute_display_column): New function to help with
	multibyte awareness in diagnostics.
	(test_cpp_utf8): New self-test.
	(input_c_tests): Call the new test.
	* input.h (location_compute_display_column): Declare.
	* diagnostic-show-locus.c: Pervasive changes to add multibyte awareness
	to all classes and functions.
	(enum column_unit): New enum.
	(class exploc_with_display_col): New class.
	(class layout_point): Convert m_column member to array m_columns[2].
	(layout_range::contains_point): Add col_unit argument.
	(test_layout_range_for_single_point): Pass new argument.
	(test_layout_range_for_single_line): Likewise.
	(test_layout_range_for_multiple_lines): Likewise.
	(line_bounds::convert_to_display_cols): New function.
	(layout::get_state_at_point): Add col_unit argument.
	(make_range): Use empty filename rather than dummy filename.
	(get_line_width_without_trailing_whitespace): Rename to...
	(get_line_bytes_without_trailing_whitespace): ...this.
	(test_get_line_width_without_trailing_whitespace): Rename to...
	(test_get_line_bytes_without_trailing_whitespace): ...this.
	(class layout): m_exploc changed to exploc_with_display_col from
	plain expanded_location.
	(layout::get_linenum_width): New accessor member function.
	(layout::get_x_offset_display): Likewise.
	(layout::calculate_linenum_width): New subroutine for the constuctor.
	(layout::calculate_x_offset_display): Likewise.
	(layout::layout): Use the new subroutines. Add multibyte awareness.
	(layout::print_source_line): Add multibyte awareness.
	(layout::print_line): Likewise.
	(layout::print_annotation_line): Likewise.
	(line_label::line_label): Likewise.
	(layout::print_any_labels): Likewise.
	(layout::annotation_line_showed_range_p): Likewise.
	(get_printed_columns): Likewise.
	(class line_label): Rename m_length to m_display_width.
	(get_affected_columns): Rename to...
	(get_affected_range): ...this; add col_unit argument and multibyte
	awareness.
	(class correction): Add m_affected_bytes and m_display_cols
	members.  Rename m_len to m_byte_length for clarity.  Add multibyte
	awareness throughout.
	(correction::insertion_p): Add multibyte awareness.
	(correction::compute_display_cols): New function.
	(correction::ensure_terminated): Use new member name m_byte_length.
	(line_corrections::add_hint): Add multibyte awareness.
	(layout::print_trailing_fixits): Likewise.
	(layout::get_x_bound_for_row): Likewise.
	(test_one_liner_simple_caret_utf8): New self-test analogous to the one
	with _utf8 suffix removed, testing multibyte awareness.
	(test_one_liner_caret_and_range_utf8): Likewise.
	(test_one_liner_multiple_carets_and_ranges_utf8): Likewise.
	(test_one_liner_fixit_insert_before_utf8): Likewise.
	(test_one_liner_fixit_insert_after_utf8): Likewise.
	(test_one_liner_fixit_remove_utf8): Likewise.
	(test_one_liner_fixit_replace_utf8): Likewise.
	(test_one_liner_fixit_replace_non_equal_range_utf8): Likewise.
	(test_one_liner_fixit_replace_equal_secondary_range_utf8): Likewise.
	(test_one_liner_fixit_validation_adhoc_locations_utf8): Likewise.
	(test_one_liner_many_fixits_1_utf8): Likewise.
	(test_one_liner_many_fixits_2_utf8): Likewise.
	(test_one_liner_labels_utf8): Likewise.
	(test_diagnostic_show_locus_one_liner_utf8): Likewise.
	(test_overlapped_fixit_printing_utf8): Likewise.
	(test_overlapped_fixit_printing): Adapt for changes to
	get_affected_columns, get_printed_columns and class corrections.
	(test_overlapped_fixit_printing_2): Likewise.
	(test_linenum_sep): New constant.
	(test_left_margin): Likewise.
	(test_offset_impl): Helper function for new test.
	(test_layout_x_offset_display_utf8): New test.
	(diagnostic_show_locus_c_tests): Call new tests.

gcc/testsuite/ChangeLog:

2019-12-09  Lewis Hyatt  <lhyatt@gmail.com>

	PR preprocessor/49973
	* gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
	(test_show_locus): Tweak so that expected output is the same as
	before the diagnostic-show-locus.c changes.
	* gcc.dg/cpp/pr66415-1.c: Likewise.

From-SVN: r279137

7 files changed, 1614 insertions, 207 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f4d1b47..8f5b06d 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,79 @@
+2019-12-09  Lewis Hyatt  <lhyatt@gmail.com>
+
+	PR preprocessor/49973
+	* input.c (location_compute_display_column): New function to help with
+	multibyte awareness in diagnostics.
+	(test_cpp_utf8): New self-test.
+	(input_c_tests): Call the new test.
+	* input.h (location_compute_display_column): Declare.
+	* diagnostic-show-locus.c: Pervasive changes to add multibyte awareness
+	to all classes and functions.
+	(enum column_unit): New enum.
+	(class exploc_with_display_col): New class.
+	(class layout_point): Convert m_column member to array m_columns[2].
+	(layout_range::contains_point): Add col_unit argument.
+	(test_layout_range_for_single_point): Pass new argument.
+	(test_layout_range_for_single_line): Likewise.
+	(test_layout_range_for_multiple_lines): Likewise.
+	(line_bounds::convert_to_display_cols): New function.
+	(layout::get_state_at_point): Add col_unit argument.
+	(make_range): Use empty filename rather than dummy filename.
+	(get_line_width_without_trailing_whitespace): Rename to...
+	(get_line_bytes_without_trailing_whitespace): ...this.
+	(test_get_line_width_without_trailing_whitespace): Rename to...
+	(test_get_line_bytes_without_trailing_whitespace): ...this.
+	(class layout): m_exploc changed to exploc_with_display_col from
+	plain expanded_location.
+	(layout::get_linenum_width): New accessor member function.
+	(layout::get_x_offset_display): Likewise.
+	(layout::calculate_linenum_width): New subroutine for the constuctor.
+	(layout::calculate_x_offset_display): Likewise.
+	(layout::layout): Use the new subroutines. Add multibyte awareness.
+	(layout::print_source_line): Add multibyte awareness.
+	(layout::print_line): Likewise.
+	(layout::print_annotation_line): Likewise.
+	(line_label::line_label): Likewise.
+	(layout::print_any_labels): Likewise.
+	(layout::annotation_line_showed_range_p): Likewise.
+	(get_printed_columns): Likewise.
+	(class line_label): Rename m_length to m_display_width.
+	(get_affected_columns): Rename to...
+	(get_affected_range): ...this; add col_unit argument and multibyte
+	awareness.
+	(class correction): Add m_affected_bytes and m_display_cols
+	members.  Rename m_len to m_byte_length for clarity.  Add multibyte
+	awareness throughout.
+	(correction::insertion_p): Add multibyte awareness.
+	(correction::compute_display_cols): New function.
+	(correction::ensure_terminated): Use new member name m_byte_length.
+	(line_corrections::add_hint): Add multibyte awareness.
+	(layout::print_trailing_fixits): Likewise.
+	(layout::get_x_bound_for_row): Likewise.
+	(test_one_liner_simple_caret_utf8): New self-test analogous to the one
+	with _utf8 suffix removed, testing multibyte awareness.
+	(test_one_liner_caret_and_range_utf8): Likewise.
+	(test_one_liner_multiple_carets_and_ranges_utf8): Likewise.
+	(test_one_liner_fixit_insert_before_utf8): Likewise.
+	(test_one_liner_fixit_insert_after_utf8): Likewise.
+	(test_one_liner_fixit_remove_utf8): Likewise.
+	(test_one_liner_fixit_replace_utf8): Likewise.
+	(test_one_liner_fixit_replace_non_equal_range_utf8): Likewise.
+	(test_one_liner_fixit_replace_equal_secondary_range_utf8): Likewise.
+	(test_one_liner_fixit_validation_adhoc_locations_utf8): Likewise.
+	(test_one_liner_many_fixits_1_utf8): Likewise.
+	(test_one_liner_many_fixits_2_utf8): Likewise.
+	(test_one_liner_labels_utf8): Likewise.
+	(test_diagnostic_show_locus_one_liner_utf8): Likewise.
+	(test_overlapped_fixit_printing_utf8): Likewise.
+	(test_overlapped_fixit_printing): Adapt for changes to
+	get_affected_columns, get_printed_columns and class corrections.
+	(test_overlapped_fixit_printing_2): Likewise.
+	(test_linenum_sep): New constant.
+	(test_left_margin): Likewise.
+	(test_offset_impl): Helper function for new test.
+	(test_layout_x_offset_display_utf8): New test.
+	(diagnostic_show_locus_c_tests): Call new tests.
+
 2019-12-09  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* tree.c (build_array_type_1): Add SET_CANONICAL parameter and compute
diff --git a/gcc/diagnostic-show-locus.c b/gcc/diagnostic-show-locus.c
index cb920f6..9cd1695 100644
--- a/gcc/diagnostic-show-locus.c
+++ b/gcc/diagnostic-show-locus.c
@@ -30,6 +30,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "gcc-rich-location.h"
 #include "selftest.h"
 #include "selftest-diagnostic.h"
+#include "cpplib.h"
 
 #ifdef HAVE_TERMIOS_H
 # include <termios.h>
@@ -112,18 +113,81 @@ class colorizer
   const char *m_stop_color;
 };
 
-/* A point within a layout_range; similar to an expanded_location,
+/* In order to handle multibyte sources properly, all of this logic needs to be
+   aware of the distinction between the number of bytes and the number of
+   display columns occupied by a character, which are not the same for non-ASCII
+   characters.  For example, the Unicode pi symbol, U+03C0, is encoded in UTF-8
+   as "\xcf\x80", and thus occupies 2 bytes of space while only occupying 1
+   display column when it is output.  A typical emoji, such as U+1F602 (in
+   UTF-8, "\xf0\x9f\x98\x82"), requires 4 bytes and has a display width of 2.
+
+   The below example line, which is also used for selftests below, shows how the
+   display column and byte column are related:
+
+     0000000001111111111222222   display
+     1234567890123456789012345   columns
+     SS_foo = P_bar.SS_fieldP;
+     0000000111111111222222223   byte
+     1356789012456789134567891   columns
+
+   Here SS represents the two display columns for the U+1F602 emoji, and P
+   represents the one display column for the U+03C0 pi symbol.  As an example, a
+   diagnostic pointing to the final P on this line is at byte column 29 and
+   display column 24.  This reflects the fact that the three extended characters
+   before the final P occupy cumulatively 5 more bytes than they do display
+   columns (a difference of 2 for each of the two SSs, and one for the other P).
+
+   One or the other of the two column units is more useful depending on the
+   context.  For instance, in order to output the caret at the correct location,
+   we need to count display columns; in order to colorize a source line, we need
+   to count the bytes.  All locations are provided to us as byte counts, which
+   we augment with the display column on demand so that it can be used when
+   needed.  This is not the most efficient way to do things since it requires
+   looping over the whole line each time, but it should be fine for the purpose
+   of outputting diagnostics.
+
+   In order to keep straight which units (byte or display) are in use at a
+   given time, the following enum lets us specify that explicitly.  */
+
+enum column_unit {
+  /* Measured in raw bytes.  */
+  CU_BYTES = 0,
+
+  /* Measured in display units.  */
+  CU_DISPLAY_COLS,
+
+  /* For arrays indexed by column_unit.  */
+  CU_NUM_UNITS
+};
+
+/* Utility class to augment an exploc with the corresponding display column.  */
+
+class exploc_with_display_col : public expanded_location
+{
+ public:
+  exploc_with_display_col (const expanded_location &exploc)
+    : expanded_location (exploc),
+      m_display_col (location_compute_display_column (exploc)) {}
+
+  int m_display_col;
+};
+
+
+/* A point within a layout_range; similar to an exploc_with_display_col,
    but after filtering on file.  */
 
 class layout_point
 {
  public:
   layout_point (const expanded_location &exploc)
-  : m_line (exploc.line),
-    m_column (exploc.column) {}
+    : m_line (exploc.line)
+  {
+    m_columns[CU_BYTES] = exploc.column;
+    m_columns[CU_DISPLAY_COLS] = location_compute_display_column (exploc);
+  }
 
   linenum_type m_line;
-  int m_column;
+  int m_columns[CU_NUM_UNITS];
 };
 
 /* A class for use by "class layout" below: a filtered location_range.  */
@@ -138,7 +202,8 @@ class layout_range
 		unsigned original_idx,
 		const range_label *label);
 
-  bool contains_point (linenum_type row, int column) const;
+  bool contains_point (linenum_type row, int column,
+		       enum column_unit col_unit) const;
   bool intersects_line_p (linenum_type row) const;
 
   layout_point m_start;
@@ -157,6 +222,17 @@ struct line_bounds
 {
   int m_first_non_ws;
   int m_last_non_ws;
+
+  void convert_to_display_cols (char_span line)
+  {
+    m_first_non_ws = cpp_byte_column_to_display_column (line.get_buffer (),
+							line.length (),
+							m_first_non_ws);
+
+    m_last_non_ws = cpp_byte_column_to_display_column (line.get_buffer (),
+						       line.length (),
+						       m_last_non_ws);
+  }
 };
 
 /* A range of contiguous source lines within a layout (e.g. "lines 5-10"
@@ -252,6 +328,9 @@ class layout
   int get_num_line_spans () const { return m_line_spans.length (); }
   const line_span *get_line_span (int idx) const { return &m_line_spans[idx]; }
 
+  int get_linenum_width () const { return m_linenum_width; }
+  int get_x_offset_display () const { return m_x_offset_display; }
+
   void print_gap_in_line_numbering ();
   bool print_heading_for_line_span_index_p (int line_span_idx) const;
 
@@ -262,7 +341,7 @@ class layout
  private:
   bool will_show_line_p (linenum_type row) const;
   void print_leading_fixits (linenum_type row);
-  void print_source_line (linenum_type row, const char *line, int line_width,
+  void print_source_line (linenum_type row, const char *line, int line_bytes,
 			  line_bounds *lbounds_out);
   bool should_print_annotation_line_p (linenum_type row) const;
   void start_annotation_line (char margin_char = ' ') const;
@@ -277,6 +356,8 @@ class layout
   bool validate_fixit_hint_p (const fixit_hint *hint);
 
   void calculate_line_spans ();
+  void calculate_linenum_width ();
+  void calculate_x_offset_display ();
 
   void print_newline ();
 
@@ -284,6 +365,7 @@ class layout
   get_state_at_point (/* Inputs.  */
 		      linenum_type row, int column,
 		      int first_non_ws, int last_non_ws,
+		      enum column_unit col_unit,
 		      /* Outputs.  */
 		      point_state *out_state);
 
@@ -298,7 +380,7 @@ class layout
   diagnostic_context *m_context;
   pretty_printer *m_pp;
   location_t m_primary_loc;
-  expanded_location m_exploc;
+  exploc_with_display_col m_exploc;
   colorizer m_colorizer;
   bool m_colorize_source_p;
   bool m_show_labels_p;
@@ -307,7 +389,7 @@ class layout
   auto_vec <const fixit_hint *> m_fixit_hints;
   auto_vec <line_span> m_line_spans;
   int m_linenum_width;
-  int m_x_offset;
+  int m_x_offset_display;
 };
 
 /* Implementation of "class colorizer".  */
@@ -472,10 +554,15 @@ layout_range::layout_range (const expanded_location *start_exploc,
    - 'w' indicates a point within the range
    - 'F' indicates the finish of the range (which is
 	 within it).
-   - 'a' indicates a subsequent point *after* the range.  */
+   - 'a' indicates a subsequent point *after* the range.
+
+   COL_UNIT controls whether we check the byte column or
+   the display column; one or the other is more convenient
+   depending on the context.  */
 
 bool
-layout_range::contains_point (linenum_type row, int column) const
+layout_range::contains_point (linenum_type row, int column,
+			      enum column_unit col_unit) const
 {
   gcc_assert (m_start.m_line <= m_finish.m_line);
   /* ...but the equivalent isn't true for the columns;
@@ -491,7 +578,7 @@ layout_range::contains_point (linenum_type row, int column) const
     /* On same line as start of range (corresponding
        to line 02 in example A and line 03 in example B).  */
     {
-      if (column < m_start.m_column)
+      if (column < m_start.m_columns[col_unit])
 	/* Points on the starting line of the range, but
 	   before the column in which it begins.  */
 	return false;
@@ -505,7 +592,7 @@ layout_range::contains_point (linenum_type row, int column) const
 	{
 	  /* This is a single-line range.  */
 	  gcc_assert (row == m_finish.m_line);
-	  return column <= m_finish.m_column;
+	  return column <= m_finish.m_columns[col_unit];
 	}
     }
 
@@ -530,7 +617,7 @@ layout_range::contains_point (linenum_type row, int column) const
 
   gcc_assert (row ==  m_finish.m_line);
 
-  return column <= m_finish.m_column;
+  return column <= m_finish.m_columns[col_unit];
 }
 
 /* Does this layout_range contain any part of line ROW?  */
@@ -548,15 +635,22 @@ layout_range::intersects_line_p (linenum_type row) const
 
 #if CHECKING_P
 
-/* A helper function for testing layout_range.  */
+/* Create some expanded locations for testing layout_range.  The filename
+   member of the explocs is set to the empty string.  This member will only be
+   inspected by the calls to location_compute_display_column() made from the
+   layout_point constructors.  That function will check for an empty filename
+   argument and not attempt to open it, rather treating the non-existent data
+   as if the display width were the same as the byte count.  Tests exercising a
+   real difference between byte count and display width are performed later,
+   e.g. in test_diagnostic_show_locus_one_liner_utf8().  */
 
 static layout_range
 make_range (int start_line, int start_col, int end_line, int end_col)
 {
   const expanded_location start_exploc
-    = {"test.c", start_line, start_col, NULL, false};
+    = {"", start_line, start_col, NULL, false};
   const expanded_location finish_exploc
-    = {"test.c", end_line, end_col, NULL, false};
+    = {"", end_line, end_col, NULL, false};
   return layout_range (&start_exploc, &finish_exploc, SHOW_RANGE_WITHOUT_CARET,
 		       &start_exploc, 0, NULL);
 }
@@ -574,20 +668,25 @@ test_layout_range_for_single_point ()
 
   /* Tests for layout_range::contains_point.  */
 
-  /* Before the line. */
-  ASSERT_FALSE (point.contains_point (6, 1));
+  for (int i = 0; i != CU_NUM_UNITS; ++i)
+    {
+      const enum column_unit col_unit = (enum column_unit) i;
 
-  /* On the line, but before start.  */
-  ASSERT_FALSE (point.contains_point (7, 9));
+      /* Before the line.  */
+      ASSERT_FALSE (point.contains_point (6, 1, col_unit));
 
-  /* At the point.  */
-  ASSERT_TRUE (point.contains_point (7, 10));
+      /* On the line, but before start.  */
+      ASSERT_FALSE (point.contains_point (7, 9, col_unit));
 
-  /* On the line, after the point.  */
-  ASSERT_FALSE (point.contains_point (7, 11));
+      /* At the point.  */
+      ASSERT_TRUE (point.contains_point (7, 10, col_unit));
 
-  /* After the line.  */
-  ASSERT_FALSE (point.contains_point (8, 1));
+      /* On the line, after the point.  */
+      ASSERT_FALSE (point.contains_point (7, 11, col_unit));
+
+      /* After the line.  */
+      ASSERT_FALSE (point.contains_point (8, 1, col_unit));
+    }
 
   /* Tests for layout_range::intersects_line_p.  */
   ASSERT_FALSE (point.intersects_line_p (6));
@@ -605,26 +704,31 @@ test_layout_range_for_single_line ()
 
   /* Tests for layout_range::contains_point.  */
 
-  /* Before the line. */
-  ASSERT_FALSE (example_a.contains_point (1, 1));
+  for (int i = 0; i != CU_NUM_UNITS; ++i)
+    {
+      const enum column_unit col_unit = (enum column_unit) i;
 
-  /* On the line, but before start.  */
-  ASSERT_FALSE (example_a.contains_point (2, 21));
+      /* Before the line.  */
+      ASSERT_FALSE (example_a.contains_point (1, 1, col_unit));
 
-  /* On the line, at the start.  */
-  ASSERT_TRUE (example_a.contains_point (2, 22));
+      /* On the line, but before start.  */
+      ASSERT_FALSE (example_a.contains_point (2, 21, col_unit));
 
-  /* On the line, within the range.  */
-  ASSERT_TRUE (example_a.contains_point (2, 23));
+      /* On the line, at the start.  */
+      ASSERT_TRUE (example_a.contains_point (2, 22, col_unit));
 
-  /* On the line, at the end.  */
-  ASSERT_TRUE (example_a.contains_point (2, 38));
+      /* On the line, within the range.  */
+      ASSERT_TRUE (example_a.contains_point (2, 23, col_unit));
 
-  /* On the line, after the end.  */
-  ASSERT_FALSE (example_a.contains_point (2, 39));
+      /* On the line, at the end.  */
+      ASSERT_TRUE (example_a.contains_point (2, 38, col_unit));
 
-  /* After the line.  */
-  ASSERT_FALSE (example_a.contains_point (2, 39));
+      /* On the line, after the end.  */
+      ASSERT_FALSE (example_a.contains_point (2, 39, col_unit));
+
+      /* After the line.  */
+      ASSERT_FALSE (example_a.contains_point (2, 39, col_unit));
+    }
 
   /* Tests for layout_range::intersects_line_p.  */
   ASSERT_FALSE (example_a.intersects_line_p (1));
@@ -642,40 +746,45 @@ test_layout_range_for_multiple_lines ()
 
   /* Tests for layout_range::contains_point.  */
 
-  /* Before first line. */
-  ASSERT_FALSE (example_b.contains_point (1, 1));
+  for (int i = 0; i != CU_NUM_UNITS; ++i)
+    {
+      const enum column_unit col_unit = (enum column_unit) i;
+
+      /* Before first line.  */
+      ASSERT_FALSE (example_b.contains_point (1, 1, col_unit));
 
-  /* On the first line, but before start.  */
-  ASSERT_FALSE (example_b.contains_point (3, 13));
+      /* On the first line, but before start.  */
+      ASSERT_FALSE (example_b.contains_point (3, 13, col_unit));
 
-  /* At the start.  */
-  ASSERT_TRUE (example_b.contains_point (3, 14));
+      /* At the start.  */
+      ASSERT_TRUE (example_b.contains_point (3, 14, col_unit));
 
-  /* On the first line, within the range.  */
-  ASSERT_TRUE (example_b.contains_point (3, 15));
+      /* On the first line, within the range.  */
+      ASSERT_TRUE (example_b.contains_point (3, 15, col_unit));
 
-  /* On an interior line.
-     The column number should not matter; try various boundary
-     values.  */
-  ASSERT_TRUE (example_b.contains_point (4, 1));
-  ASSERT_TRUE (example_b.contains_point (4, 7));
-  ASSERT_TRUE (example_b.contains_point (4, 8));
-  ASSERT_TRUE (example_b.contains_point (4, 9));
-  ASSERT_TRUE (example_b.contains_point (4, 13));
-  ASSERT_TRUE (example_b.contains_point (4, 14));
-  ASSERT_TRUE (example_b.contains_point (4, 15));
+      /* On an interior line.
+	 The column number should not matter; try various boundary
+	 values.  */
+      ASSERT_TRUE (example_b.contains_point (4, 1, col_unit));
+      ASSERT_TRUE (example_b.contains_point (4, 7, col_unit));
+      ASSERT_TRUE (example_b.contains_point (4, 8, col_unit));
+      ASSERT_TRUE (example_b.contains_point (4, 9, col_unit));
+      ASSERT_TRUE (example_b.contains_point (4, 13, col_unit));
+      ASSERT_TRUE (example_b.contains_point (4, 14, col_unit));
+      ASSERT_TRUE (example_b.contains_point (4, 15, col_unit));
 
-  /* On the final line, before the end.  */
-  ASSERT_TRUE (example_b.contains_point (5, 7));
+      /* On the final line, before the end.  */
+      ASSERT_TRUE (example_b.contains_point (5, 7, col_unit));
 
-  /* On the final line, at the end.  */
-  ASSERT_TRUE (example_b.contains_point (5, 8));
+      /* On the final line, at the end.  */
+      ASSERT_TRUE (example_b.contains_point (5, 8, col_unit));
 
-  /* On the final line, after the end.  */
-  ASSERT_FALSE (example_b.contains_point (5, 9));
+      /* On the final line, after the end.  */
+      ASSERT_FALSE (example_b.contains_point (5, 9, col_unit));
 
-  /* After the line.  */
-  ASSERT_FALSE (example_b.contains_point (6, 1));
+      /* After the line.  */
+      ASSERT_FALSE (example_b.contains_point (6, 1, col_unit));
+    }
 
   /* Tests for layout_range::intersects_line_p.  */
   ASSERT_FALSE (example_b.intersects_line_p (2));
@@ -687,13 +796,13 @@ test_layout_range_for_multiple_lines ()
 
 #endif /* #if CHECKING_P */
 
-/* Given a source line LINE of length LINE_WIDTH, determine the width
-   without any trailing whitespace.  */
+/* Given a source line LINE of length LINE_BYTES bytes, determine the length
+   (still in bytes, not display cols) without any trailing whitespace.  */
 
 static int
-get_line_width_without_trailing_whitespace (const char *line, int line_width)
+get_line_bytes_without_trailing_whitespace (const char *line, int line_bytes)
 {
-  int result = line_width;
+  int result = line_bytes;
   while (result > 0)
     {
       char ch = line[result - 1];
@@ -703,7 +812,7 @@ get_line_width_without_trailing_whitespace (const char *line, int line_width)
 	break;
     }
   gcc_assert (result >= 0);
-  gcc_assert (result <= line_width);
+  gcc_assert (result <= line_bytes);
   gcc_assert (result == 0 ||
 	      (line[result - 1] != ' '
 	       && line[result -1] != '\t'
@@ -713,21 +822,21 @@ get_line_width_without_trailing_whitespace (const char *line, int line_width)
 
 #if CHECKING_P
 
-/* A helper function for testing get_line_width_without_trailing_whitespace.  */
+/* A helper function for testing get_line_bytes_without_trailing_whitespace.  */
 
 static void
-assert_eq (const char *line, int expected_width)
+assert_eq (const char *line, int expected_bytes)
 {
   int actual_value
-    = get_line_width_without_trailing_whitespace (line, strlen (line));
-  ASSERT_EQ (actual_value, expected_width);
+    = get_line_bytes_without_trailing_whitespace (line, strlen (line));
+  ASSERT_EQ (actual_value, expected_bytes);
 }
 
-/* Verify that get_line_width_without_trailing_whitespace is sane for
+/* Verify that get_line_bytes_without_trailing_whitespace is sane for
    various inputs.  It is not required to handle newlines.  */
 
 static void
-test_get_line_width_without_trailing_whitespace ()
+test_get_line_bytes_without_trailing_whitespace ()
 {
   assert_eq ("", 0);
   assert_eq (" ", 0);
@@ -835,7 +944,7 @@ fixit_cmp (const void *p_a, const void *p_b)
    sanely print, populating m_layout_ranges and m_fixit_hints.
    Determine the range of lines that we will print, splitting them
    up into an ordered list of disjoint spans of contiguous line numbers.
-   Determine m_x_offset, to ensure that the primary caret
+   Determine m_x_offset_display, to ensure that the primary caret
    will fit within the max_width provided by the diagnostic_context.  */
 
 layout::layout (diagnostic_context * context,
@@ -853,7 +962,7 @@ layout::layout (diagnostic_context * context,
   m_fixit_hints (richloc->get_num_fixit_hints ()),
   m_line_spans (1 + richloc->get_num_locations ()),
   m_linenum_width (0),
-  m_x_offset (0)
+  m_x_offset_display (0)
 {
   for (unsigned int idx = 0; idx < richloc->get_num_locations (); idx++)
     {
@@ -875,45 +984,16 @@ layout::layout (diagnostic_context * context,
   /* Sort m_fixit_hints.  */
   m_fixit_hints.qsort (fixit_cmp);
 
-  /* Populate m_line_spans.  */
+  /* Populate the indicated members.  */
   calculate_line_spans ();
-
-  /* Determine m_linenum_width.  */
-  gcc_assert (m_line_spans.length () > 0);
-  const line_span *last_span = &m_line_spans[m_line_spans.length () - 1];
-  int highest_line = last_span->m_last_line;
-  if (highest_line < 0)
-    highest_line = 0;
-  m_linenum_width = num_digits (highest_line);
-  /* If we're showing jumps in the line-numbering, allow at least 3 chars.  */
-  if (m_line_spans.length () > 1)
-    m_linenum_width = MAX (m_linenum_width, 3);
-  /* If there's a minimum margin width, apply it (subtracting 1 for the space
-     after the line number.  */
-  m_linenum_width = MAX (m_linenum_width, context->min_margin_width - 1);
-
-  /* Adjust m_x_offset.
-     Center the primary caret to fit in max_width; all columns
-     will be adjusted accordingly.  */
-  size_t max_width = m_context->caret_max_width;
-  char_span line = location_get_source_line (m_exploc.file, m_exploc.line);
-  if (line && (size_t)m_exploc.column <= line.length ())
-    {
-      size_t right_margin = CARET_LINE_MARGIN;
-      size_t column = m_exploc.column;
-      if (m_show_line_numbers_p)
-	column += m_linenum_width + 2;
-      right_margin = MIN (line.length () - column, right_margin);
-      right_margin = max_width - right_margin;
-      if (line.length () >= max_width && column > right_margin)
-	m_x_offset = column - right_margin;
-      gcc_assert (m_x_offset >= 0);
-    }
+  calculate_linenum_width ();
+  calculate_x_offset_display ();
 
   if (context->show_ruler_p)
-    show_ruler (m_x_offset + max_width);
+    show_ruler (m_x_offset_display + m_context->caret_max_width);
 }
 
+
 /* Attempt to add LOC_RANGE to m_layout_ranges, filtering them to
    those that we can sanely print.
 
@@ -1086,7 +1166,7 @@ layout::get_expanded_location (const line_span *line_span) const
 	{
 	  expanded_location exploc = m_exploc;
 	  exploc.line = lr->m_start.m_line;
-	  exploc.column = lr->m_start.m_column;
+	  exploc.column = lr->m_start.m_columns[CU_BYTES];
 	  return exploc;
 	}
     }
@@ -1251,25 +1331,122 @@ layout::calculate_line_spans ()
     }
 }
 
+/* Determine how many display columns need to be reserved for line numbers,
+   based on the largest line number that will be needed, and populate
+   m_linenum_width.  */
+
+void
+layout::calculate_linenum_width ()
+{
+  gcc_assert (m_line_spans.length () > 0);
+  const line_span *last_span = &m_line_spans[m_line_spans.length () - 1];
+  int highest_line = last_span->m_last_line;
+  if (highest_line < 0)
+    highest_line = 0;
+  m_linenum_width = num_digits (highest_line);
+  /* If we're showing jumps in the line-numbering, allow at least 3 chars.  */
+  if (m_line_spans.length () > 1)
+    m_linenum_width = MAX (m_linenum_width, 3);
+  /* If there's a minimum margin width, apply it (subtracting 1 for the space
+     after the line number.  */
+  m_linenum_width = MAX (m_linenum_width, m_context->min_margin_width - 1);
+}
+
+/* Calculate m_x_offset_display, which improves readability in case the source
+   line of interest is longer than the user's display.  All lines output will be
+   shifted to the left (so that their beginning is no longer displayed) by
+   m_x_offset_display display columns, so that the caret is in a reasonable
+   location.  */
+
+void
+layout::calculate_x_offset_display ()
+{
+  m_x_offset_display = 0;
+
+  const int max_width = m_context->caret_max_width;
+  if (!max_width)
+    {
+      /* Nothing to do, the width is not capped.  */
+      return;
+    }
+
+  const char_span line = location_get_source_line (m_exploc.file,
+						   m_exploc.line);
+  if (!line)
+    {
+      /* Nothing to do, we couldn't find the source line.  */
+      return;
+    }
+  int caret_display_column = m_exploc.m_display_col;
+  const int line_bytes
+    = get_line_bytes_without_trailing_whitespace (line.get_buffer (),
+						  line.length ());
+  int eol_display_column
+    = cpp_display_width (line.get_buffer (), line_bytes);
+  if (caret_display_column > eol_display_column
+      || !caret_display_column)
+    {
+      /* This does not make sense, so don't try to do anything in this case.  */
+      return;
+    }
+
+  /* Adjust caret and eol positions to include the left margin.  If we are
+     outputting line numbers, then the left margin is equal to m_linenum_width
+     plus three for the " | " which follows it.  Otherwise the left margin width
+     is equal to 1, because layout::print_source_line() will prefix each line
+     with a space.  */
+  const int source_display_cols = eol_display_column;
+  int left_margin_size = 1;
+  if (m_show_line_numbers_p)
+      left_margin_size = m_linenum_width + 3;
+  caret_display_column += left_margin_size;
+  eol_display_column += left_margin_size;
+
+  if (eol_display_column <= max_width)
+    {
+      /* Nothing to do, everything fits in the display.  */
+      return;
+    }
+
+  /* The line is too long for the display.  Calculate an offset such that the
+     caret is not too close to the right edge of the screen.  It will be
+     CARET_LINE_MARGIN display columns from the right edge, unless it is closer
+     than that to the end of the source line anyway.  */
+  int right_margin_size = CARET_LINE_MARGIN;
+  right_margin_size = MIN (eol_display_column - caret_display_column,
+			   right_margin_size);
+  if (right_margin_size + left_margin_size >= max_width)
+    {
+      /* The max_width is very small, so anything we try to do will not be very
+	 effective; just punt in this case and output with no offset.  */
+      return;
+    }
+  const int max_caret_display_column = max_width - right_margin_size;
+  if (caret_display_column > max_caret_display_column)
+    {
+      m_x_offset_display = caret_display_column - max_caret_display_column;
+      /* Make sure we don't offset the line into oblivion.  */
+      static const int min_cols_visible = 2;
+      if (source_display_cols - m_x_offset_display < min_cols_visible)
+	m_x_offset_display = 0;
+    }
+}
+
 /* Print line ROW of source code, potentially colorized at any ranges, and
    populate *LBOUNDS_OUT.
-   LINE is the source line (not necessarily 0-terminated) and LINE_WIDTH
-   is its width.  */
+   LINE is the source line (not necessarily 0-terminated) and LINE_BYTES
+   is its length in bytes.
+   This function deals only with byte offsets, not display columns, so
+   m_x_offset_display must be converted from display to byte units.  In
+   particular, LINE_BYTES and LBOUNDS_OUT are in bytes.  */
 
 void
-layout::print_source_line (linenum_type row, const char *line, int line_width,
+layout::print_source_line (linenum_type row, const char *line, int line_bytes,
 			   line_bounds *lbounds_out)
 {
   m_colorizer.set_normal_text ();
 
-  /* We will stop printing the source line at any trailing
-     whitespace.  */
-  line_width = get_line_width_without_trailing_whitespace (line,
-							   line_width);
-  line += m_x_offset;
-
   pp_emit_prefix (m_pp);
-
   if (m_show_line_numbers_p)
     {
       int width = num_digits (row);
@@ -1279,10 +1456,31 @@ layout::print_source_line (linenum_type row, const char *line, int line_width,
     }
   else
     pp_space (m_pp);
+
+  /* We will stop printing the source line at any trailing whitespace, and start
+     printing it as per m_x_offset_display.  */
+  line_bytes = get_line_bytes_without_trailing_whitespace (line,
+							   line_bytes);
+  int x_offset_bytes = 0;
+  if (m_x_offset_display)
+    {
+      x_offset_bytes = cpp_display_column_to_byte_column (line, line_bytes,
+							  m_x_offset_display);
+      /* In case the leading portion of the line that will be skipped over ends
+	 with a character with wcwidth > 1, then it is possible we skipped too
+	 much, so account for that by padding with spaces.  */
+      const int overage
+	= cpp_byte_column_to_display_column (line, line_bytes, x_offset_bytes)
+	- m_x_offset_display;
+      for (int column = 0; column < overage; ++column)
+	pp_space (m_pp);
+      line += x_offset_bytes;
+    }
+
+  /* Print the line.  */
   int first_non_ws = INT_MAX;
   int last_non_ws = 0;
-  int column;
-  for (column = 1 + m_x_offset; column <= line_width; column++)
+  for (int col_byte = 1 + x_offset_bytes; col_byte <= line_bytes; col_byte++)
     {
       /* Assuming colorization is enabled for the caret and underline
 	 characters, we may also colorize the associated characters
@@ -1300,8 +1498,9 @@ layout::print_source_line (linenum_type row, const char *line, int line_width,
 	{
 	  bool in_range_p;
 	  point_state state;
-	  in_range_p = get_state_at_point (row, column,
+	  in_range_p = get_state_at_point (row, col_byte,
 					   0, INT_MAX,
+					   CU_BYTES,
 					   &state);
 	  if (in_range_p)
 	    m_colorizer.set_range (state.range_idx);
@@ -1313,9 +1512,9 @@ layout::print_source_line (linenum_type row, const char *line, int line_width,
 	c = ' ';
       if (c != ' ')
 	{
-	  last_non_ws = column;
+	  last_non_ws = col_byte;
 	  if (first_non_ws == INT_MAX)
-	    first_non_ws = column;
+	    first_non_ws = col_byte;
 	}
       pp_character (m_pp, c);
       line++;
@@ -1365,24 +1564,26 @@ layout::start_annotation_line (char margin_char) const
 }
 
 /* Print a line consisting of the caret/underlines for the given
-   source line.  */
+   source line.  This function works with display columns, rather than byte
+   counts; in particular, LBOUNDS should be in display column units.  */
 
 void
 layout::print_annotation_line (linenum_type row, const line_bounds lbounds)
 {
-  int x_bound = get_x_bound_for_row (row, m_exploc.column,
+  int x_bound = get_x_bound_for_row (row, m_exploc.m_display_col,
 				     lbounds.m_last_non_ws);
 
   start_annotation_line ();
   pp_space (m_pp);
 
-  for (int column = 1 + m_x_offset; column < x_bound; column++)
+  for (int column = 1 + m_x_offset_display; column < x_bound; column++)
     {
       bool in_range_p;
       point_state state;
       in_range_p = get_state_at_point (row, column,
 				       lbounds.m_first_non_ws,
 				       lbounds.m_last_non_ws,
+				       CU_DISPLAY_COLS,
 				       &state);
       if (in_range_p)
 	{
@@ -1420,9 +1621,11 @@ class line_label
 public:
   line_label (int state_idx, int column, label_text text)
   : m_state_idx (state_idx), m_column (column),
-    m_text (text), m_length (strlen (text.m_buffer)),
-    m_label_line (0), m_has_vbar (true)
-  {}
+    m_text (text), m_label_line (0), m_has_vbar (true)
+  {
+    const int bytes = strlen (text.m_buffer);
+    m_display_width = cpp_display_width (text.m_buffer, bytes);
+  }
 
   /* Sorting is primarily by column, then by state index.  */
   static int comparator (const void *p1, const void *p2)
@@ -1441,7 +1644,7 @@ public:
   int m_state_idx;
   int m_column;
   label_text m_text;
-  size_t m_length;
+  size_t m_display_width;
   int m_label_line;
   bool m_has_vbar;
 };
@@ -1467,8 +1670,9 @@ layout::print_any_labels (linenum_type row)
 	  continue;
 
 	/* Reject labels that aren't fully visible due to clipping
-	   by m_x_offset.  */
-	if (range->m_caret.m_column <= m_x_offset)
+	   by m_x_offset_display.  */
+	const int disp_col = range->m_caret.m_columns[CU_DISPLAY_COLS];
+	if (disp_col <= m_x_offset_display)
 	  continue;
 
 	label_text text;
@@ -1480,7 +1684,7 @@ layout::print_any_labels (linenum_type row)
 	if (text.m_buffer == NULL)
 	  continue;
 
-	labels.safe_push (line_label (i, range->m_caret.m_column, text));
+	labels.safe_push (line_label (i, disp_col, text));
       }
   }
 
@@ -1530,7 +1734,7 @@ layout::print_any_labels (linenum_type row)
     FOR_EACH_VEC_ELT_REVERSE (labels, i, label)
       {
 	/* Would this label "touch" or overlap the next label?  */
-	if (label->m_column + label->m_length >= (size_t)next_column)
+	if (label->m_column + label->m_display_width >= (size_t)next_column)
 	  {
 	    max_label_line++;
 
@@ -1554,7 +1758,7 @@ layout::print_any_labels (linenum_type row)
       {
 	start_annotation_line ();
 	pp_space (m_pp);
-	int column = 1 + m_x_offset;
+	int column = 1 + m_x_offset_display;
 	line_label *label;
 	FOR_EACH_VEC_ELT (labels, i, label)
 	  {
@@ -1569,7 +1773,7 @@ layout::print_any_labels (linenum_type row)
 		m_colorizer.set_range (label->m_state_idx);
 		pp_string (m_pp, label->m_text.m_buffer);
 		m_colorizer.set_normal_text ();
-		column += label->m_length;
+		column += label->m_display_width;
 	      }
 	    else if (label->m_has_vbar)
 	      {
@@ -1636,7 +1840,7 @@ layout::print_leading_fixits (linenum_type row)
 /* Subroutine of layout::print_trailing_fixits.
 
    Determine if the annotation line printed for LINE contained
-   the exact range from START_COLUMN to FINISH_COLUMN.  */
+   the exact range from START_COLUMN to FINISH_COLUMN (in display units).  */
 
 bool
 layout::annotation_line_showed_range_p (linenum_type line, int start_column,
@@ -1646,9 +1850,9 @@ layout::annotation_line_showed_range_p (linenum_type line, int start_column,
   int i;
   FOR_EACH_VEC_ELT (m_layout_ranges, i, range)
     if (range->m_start.m_line == line
-	&& range->m_start.m_column == start_column
+	&& range->m_start.m_columns[CU_DISPLAY_COLS] == start_column
 	&& range->m_finish.m_line == line
-	&& range->m_finish.m_column == finish_column)
+	&& range->m_finish.m_columns[CU_DISPLAY_COLS] == finish_column)
       return true;
   return false;
 }
@@ -1735,7 +1939,7 @@ layout::annotation_line_showed_range_p (linenum_type line, int start_column,
 
    and is thus printed as desired.  */
 
-/* A range of columns within a line.  */
+/* A range of (byte or display) columns within a line.  */
 
 class column_range
 {
@@ -1755,32 +1959,51 @@ public:
   int finish;
 };
 
-/* Get the range of columns that HINT would affect.  */
-
+/* Get the range of bytes or display columns that HINT would affect.  */
 static column_range
-get_affected_columns (const fixit_hint *hint)
+get_affected_range (const fixit_hint *hint, enum column_unit col_unit)
 {
-  int start_column = LOCATION_COLUMN (hint->get_start_loc ());
-  int finish_column = LOCATION_COLUMN (hint->get_next_loc ()) - 1;
+  expanded_location exploc_start = expand_location (hint->get_start_loc ());
+  expanded_location exploc_finish = expand_location (hint->get_next_loc ());
+  --exploc_finish.column;
 
+  int start_column;
+  int finish_column;
+  if (col_unit == CU_DISPLAY_COLS)
+    {
+      start_column = location_compute_display_column (exploc_start);
+      if (hint->insertion_p ())
+	finish_column = start_column - 1;
+      else
+	finish_column = location_compute_display_column (exploc_finish);
+    }
+  else
+    {
+      start_column = exploc_start.column;
+      finish_column = exploc_finish.column;
+    }
   return column_range (start_column, finish_column);
 }
 
-/* Get the range of columns that would be printed for HINT.  */
+/* Get the range of display columns that would be printed for HINT.  */
 
 static column_range
 get_printed_columns (const fixit_hint *hint)
 {
-  int start_column = LOCATION_COLUMN (hint->get_start_loc ());
-  int final_hint_column = start_column + hint->get_length () - 1;
+  expanded_location exploc = expand_location (hint->get_start_loc ());
+  int start_column = location_compute_display_column (exploc);
+  int hint_width = cpp_display_width (hint->get_string (),
+				      hint->get_length ());
+  int final_hint_column = start_column + hint_width - 1;
   if (hint->insertion_p ())
     {
       return column_range (start_column, final_hint_column);
     }
   else
     {
-      int finish_column = LOCATION_COLUMN (hint->get_next_loc ()) - 1;
-
+      exploc = expand_location (hint->get_next_loc ());
+      --exploc.column;
+      int finish_column = location_compute_display_column (exploc);
       return column_range (start_column,
 			   MAX (finish_column, final_hint_column));
     }
@@ -1794,27 +2017,35 @@ get_printed_columns (const fixit_hint *hint)
 class correction
 {
 public:
-  correction (column_range affected_columns,
+  correction (column_range affected_bytes,
+	      column_range affected_columns,
 	      column_range printed_columns,
 	      const char *new_text, size_t new_text_len)
-  : m_affected_columns (affected_columns),
+  : m_affected_bytes (affected_bytes),
+    m_affected_columns (affected_columns),
     m_printed_columns (printed_columns),
     m_text (xstrdup (new_text)),
-    m_len (new_text_len),
+    m_byte_length (new_text_len),
     m_alloc_sz (new_text_len + 1)
   {
+    compute_display_cols ();
   }
 
   ~correction () { free (m_text); }
 
   bool insertion_p () const
   {
-    return m_affected_columns.start == m_affected_columns.finish + 1;
+    return m_affected_bytes.start == m_affected_bytes.finish + 1;
   }
 
   void ensure_capacity (size_t len);
   void ensure_terminated ();
 
+  void compute_display_cols ()
+  {
+    m_display_cols = cpp_display_width (m_text, m_byte_length);
+  }
+
   void overwrite (int dst_offset, const char_span &src_span)
   {
     gcc_assert (dst_offset >= 0);
@@ -1827,6 +2058,7 @@ public:
      is to be inserted, and finish is offset by the length of
      the replacement.
      If replace, then the range of columns affected.  */
+  column_range m_affected_bytes;
   column_range m_affected_columns;
 
   /* If insert, then start: the column before which the text
@@ -1837,7 +2069,8 @@ public:
 
   /* The text to be inserted/used as replacement.  */
   char *m_text;
-  size_t m_len;
+  size_t m_byte_length; /* Not including null-terminator.  */
+  int m_display_cols;
   size_t m_alloc_sz;
 };
 
@@ -1862,8 +2095,8 @@ void
 correction::ensure_terminated ()
 {
   /* 0-terminate the buffer.  */
-  gcc_assert (m_len < m_alloc_sz);
-  m_text[m_len] = '\0';
+  gcc_assert (m_byte_length < m_alloc_sz);
+  m_text[m_byte_length] = '\0';
 }
 
 /* A list of corrections affecting a particular line.
@@ -1925,7 +2158,8 @@ source_line::source_line (const char *filename, int line)
 void
 line_corrections::add_hint (const fixit_hint *hint)
 {
-  column_range affected_columns = get_affected_columns (hint);
+  column_range affected_bytes = get_affected_range (hint, CU_BYTES);
+  column_range affected_columns = get_affected_range (hint, CU_DISPLAY_COLS);
   column_range printed_columns = get_printed_columns (hint);
 
   /* Potentially consolidate.  */
@@ -1936,8 +2170,8 @@ line_corrections::add_hint (const fixit_hint *hint)
 
       /* The following consolidation code assumes that the fix-it hints
 	 have been sorted by start (done within layout's ctor).  */
-      gcc_assert (affected_columns.start
-		  >= last_correction->m_affected_columns.start);
+      gcc_assert (affected_bytes.start
+		  >= last_correction->m_affected_bytes.start);
       gcc_assert (printed_columns.start
 		  >= last_correction->m_printed_columns.start);
 
@@ -1949,8 +2183,8 @@ line_corrections::add_hint (const fixit_hint *hint)
 	     Attempt to inject a "replace" correction from immediately
 	     after the end of the last hint to immediately before the start
 	     of the next hint.  */
-	  column_range between (last_correction->m_affected_columns.finish + 1,
-				printed_columns.start - 1);
+	  column_range between (last_correction->m_affected_bytes.finish + 1,
+				affected_bytes.start - 1);
 
 	  /* Try to read the source.  */
 	  source_line line (m_filename, m_row);
@@ -1959,33 +2193,39 @@ line_corrections::add_hint (const fixit_hint *hint)
 	      /* Consolidate into the last correction:
 		 add a no-op "replace" of the "between" text, and
 		 add the text from the new hint.  */
-	      int old_len = last_correction->m_len;
-	      gcc_assert (old_len >= 0);
-	      int between_len = between.finish + 1 - between.start;
-	      gcc_assert (between_len >= 0);
-	      int new_len = old_len + between_len + hint->get_length ();
-	      gcc_assert (new_len >= 0);
-	      last_correction->ensure_capacity (new_len);
+	      int old_byte_len = last_correction->m_byte_length;
+	      gcc_assert (old_byte_len >= 0);
+	      int between_byte_len = between.finish + 1 - between.start;
+	      gcc_assert (between_byte_len >= 0);
+	      int new_byte_len
+		= old_byte_len + between_byte_len + hint->get_length ();
+	      gcc_assert (new_byte_len >= 0);
+	      last_correction->ensure_capacity (new_byte_len);
 	      last_correction->overwrite
-		(old_len,
+		(old_byte_len,
 		 line.as_span ().subspan (between.start - 1,
 					  between.finish + 1 - between.start));
-	      last_correction->overwrite (old_len + between_len,
+	      last_correction->overwrite (old_byte_len + between_byte_len,
 					  char_span (hint->get_string (),
 						     hint->get_length ()));
-	      last_correction->m_len = new_len;
+	      last_correction->m_byte_length = new_byte_len;
 	      last_correction->ensure_terminated ();
+	      last_correction->m_affected_bytes.finish
+		= affected_bytes.finish;
 	      last_correction->m_affected_columns.finish
 		= affected_columns.finish;
+	      int prev_display_cols = last_correction->m_display_cols;
+	      last_correction->compute_display_cols ();
 	      last_correction->m_printed_columns.finish
-		+= between_len + hint->get_length ();
+		+= last_correction->m_display_cols - prev_display_cols;
 	      return;
 	    }
 	}
     }
 
   /* If no consolidation happened, add a new correction instance.  */
-  m_corrections.safe_push (new correction (affected_columns,
+  m_corrections.safe_push (new correction (affected_bytes,
+					   affected_columns,
 					   printed_columns,
 					   hint->get_string (),
 					   hint->get_length ()));
@@ -2018,7 +2258,7 @@ layout::print_trailing_fixits (linenum_type row)
   /* Now print the corrections.  */
   unsigned i;
   correction *c;
-  int column = m_x_offset;
+  int column = m_x_offset_display;
 
   if (!corrections.m_corrections.is_empty ())
     start_annotation_line ();
@@ -2034,7 +2274,7 @@ layout::print_trailing_fixits (linenum_type row)
 	  m_colorizer.set_fixit_insert ();
 	  pp_string (m_pp, c->m_text);
 	  m_colorizer.set_normal_text ();
-	  column += c->m_len;
+	  column += c->m_display_cols;
 	}
       else
 	{
@@ -2046,7 +2286,7 @@ layout::print_trailing_fixits (linenum_type row)
 	  int finish_column = c->m_affected_columns.finish;
 	  if (!annotation_line_showed_range_p (row, start_column,
 					       finish_column)
-	      || c->m_len == 0)
+	      || c->m_byte_length == 0)
 	    {
 	      move_to_column (&column, start_column, true);
 	      m_colorizer.set_fixit_delete ();
@@ -2057,13 +2297,13 @@ layout::print_trailing_fixits (linenum_type row)
 	  /* Print the replacement text.  REPLACE also covers
 	     removals, so only do this extra work (potentially starting
 	     a new line) if we have actual replacement text.  */
-	  if (c->m_len > 0)
+	  if (c->m_byte_length > 0)
 	    {
 	      move_to_column (&column, start_column, true);
 	      m_colorizer.set_fixit_insert ();
 	      pp_string (m_pp, c->m_text);
 	      m_colorizer.set_normal_text ();
-	      column += c->m_len;
+	      column += c->m_display_cols;
 	    }
 	}
     }
@@ -2084,12 +2324,14 @@ layout::print_newline ()
 /* Return true if (ROW/COLUMN) is within a range of the layout.
    If it returns true, OUT_STATE is written to, with the
    range index, and whether we should draw the caret at
-   (ROW/COLUMN) (as opposed to an underline).  */
+   (ROW/COLUMN) (as opposed to an underline).  COL_UNIT controls
+   whether all inputs and outputs are in bytes or display column units.  */
 
 bool
 layout::get_state_at_point (/* Inputs.  */
 			    linenum_type row, int column,
 			    int first_non_ws, int last_non_ws,
+			    enum column_unit col_unit,
 			    /* Outputs.  */
 			    point_state *out_state)
 {
@@ -2102,7 +2344,7 @@ layout::get_state_at_point (/* Inputs.  */
 	   source colorization.  */
 	continue;
 
-      if (range->contains_point (row, column))
+      if (range->contains_point (row, column, col_unit))
 	{
 	  out_state->range_idx = i;
 
@@ -2110,7 +2352,7 @@ layout::get_state_at_point (/* Inputs.  */
 	  out_state->draw_caret_p = false;
 	  if (range->m_range_display_kind == SHOW_RANGE_WITH_CARET
 	      && row == range->m_caret.m_line
-	      && column == range->m_caret.m_column)
+	      && column == range->m_caret.m_columns[col_unit])
 	    out_state->draw_caret_p = true;
 
 	  /* Within a multiline range, don't display any underline
@@ -2130,11 +2372,11 @@ layout::get_state_at_point (/* Inputs.  */
 
 /* Helper function for use by layout::print_line when printing the
    annotation line under the source line.
-   Get the column beyond the rightmost one that could contain a caret or
-   range marker, given that we stop rendering at trailing whitespace.
+   Get the display column beyond the rightmost one that could contain a caret
+   or range marker, given that we stop rendering at trailing whitespace.
    ROW is the source line within the given file.
-   CARET_COLUMN is the column of range 0's caret.
-   LAST_NON_WS_COLUMN is the last column containing a non-whitespace
+   CARET_COLUMN is the display column of range 0's caret.
+   LAST_NON_WS_COLUMN is the last display column containing a non-whitespace
    character of source (as determined when printing the source line).  */
 
 int
@@ -2153,8 +2395,9 @@ layout::get_x_bound_for_row (linenum_type row, int caret_column,
 	    {
 	      /* On the final line within a range; ensure that
 		 we render up to the end of the range.  */
-	      if (result <= range->m_finish.m_column)
-		result = range->m_finish.m_column + 1;
+	      const int disp_col = range->m_finish.m_columns[CU_DISPLAY_COLS];
+	      if (result <= disp_col)
+		result = disp_col + 1;
 	    }
 	  else if (row < range->m_finish.m_line)
 	    {
@@ -2183,7 +2426,7 @@ layout::move_to_column (int *column, int dest_column, bool add_left_margin)
       print_newline ();
       if (add_left_margin)
 	start_annotation_line ();
-      *column = m_x_offset;
+      *column = m_x_offset_display;
     }
 
   while (*column < dest_column)
@@ -2204,7 +2447,7 @@ layout::show_ruler (int max_column) const
     {
       start_annotation_line ();
       pp_space (m_pp);
-      for (int column = 1 + m_x_offset; column <= max_column; column++)
+      for (int column = 1 + m_x_offset_display; column <= max_column; column++)
 	if (column % 10 == 0)
 	  pp_character (m_pp, '0' + (column / 100) % 10);
 	else
@@ -2215,7 +2458,7 @@ layout::show_ruler (int max_column) const
   /* Tens.  */
   start_annotation_line ();
   pp_space (m_pp);
-  for (int column = 1 + m_x_offset; column <= max_column; column++)
+  for (int column = 1 + m_x_offset_display; column <= max_column; column++)
     if (column % 10 == 0)
       pp_character (m_pp, '0' + (column / 10) % 10);
     else
@@ -2225,7 +2468,7 @@ layout::show_ruler (int max_column) const
   /* Units.  */
   start_annotation_line ();
   pp_space (m_pp);
-  for (int column = 1 + m_x_offset; column <= max_column; column++)
+  for (int column = 1 + m_x_offset_display; column <= max_column; column++)
     pp_character (m_pp, '0' + (column % 10));
   pp_newline (m_pp);
 }
@@ -2245,7 +2488,11 @@ layout::print_line (linenum_type row)
   print_leading_fixits (row);
   print_source_line (row, line.get_buffer (), line.length (), &lbounds);
   if (should_print_annotation_line_p (row))
-    print_annotation_line (row, lbounds);
+    {
+      if (lbounds.m_first_non_ws != INT_MAX)
+	lbounds.convert_to_display_cols (line);
+      print_annotation_line (row, lbounds);
+    }
   if (m_show_labels_p)
     print_any_labels (row);
   print_trailing_fixits (row);
@@ -2339,6 +2586,178 @@ namespace selftest {
 
 /* Selftests for diagnostic_show_locus.  */
 
+/* For precise tests of the layout, make clear where the source line will
+   start.  test_left_margin sets the total byte count from the left side of the
+   screen to the start of source lines, after the line number and the separator,
+   which consists of the three characters " | ".  */
+static const int test_linenum_sep = 3;
+static const int test_left_margin = 7;
+
+/* Helper function for test_layout_x_offset_display_utf8().  */
+static void
+test_offset_impl (int caret_byte_col, int max_width,
+		  int expected_x_offset_display,
+		  int left_margin = test_left_margin)
+{
+  test_diagnostic_context dc;
+  dc.caret_max_width = max_width;
+  /* diagnostic_context::min_margin_width sets the minimum space reserved for
+     the line number plus one space after.  */
+  dc.min_margin_width = left_margin - test_linenum_sep + 1;
+  dc.show_line_numbers_p = true;
+  rich_location richloc (line_table,
+			 linemap_position_for_column (line_table,
+						      caret_byte_col));
+  layout test_layout (&dc, &richloc, DK_ERROR);
+  ASSERT_EQ (left_margin - test_linenum_sep,
+	     test_layout.get_linenum_width ());
+  ASSERT_EQ (expected_x_offset_display,
+	     test_layout.get_x_offset_display ());
+}
+
+/* Test that layout::calculate_x_offset_display() works.  */
+static void
+test_layout_x_offset_display_utf8 (const line_table_case &case_)
+{
+
+  const char *content
+    = "This line is very long, so that we can use it to test the logic for "
+      "clipping long lines.  Also this: \xf0\x9f\x98\x82\xf0\x9f\x98\x82 is a "
+      "pair of emojis that occupies 8 bytes and 4 display columns, starting at "
+      "column #102.\n";
+
+  /* Number of bytes in the line, subtracting one to remove the newline.  */
+  const int line_bytes = strlen (content) - 1;
+
+  /* Number of display columns occupied by the line; each of the 2 emojis
+     takes up 2 fewer display columns than it does bytes.  */
+  const int line_display_cols = line_bytes - 2*2;
+
+  /* The column of the first emoji.  Byte or display is the same as there are
+     no multibyte characters earlier on the line.  */
+  const int emoji_col = 102;
+
+  temp_source_file tmp (SELFTEST_LOCATION, ".c", content);
+  line_table_test ltt (case_);
+
+  linemap_add (line_table, LC_ENTER, false, tmp.get_filename (), 1);
+
+  location_t line_end = linemap_position_for_column (line_table, line_bytes);
+
+  /* Don't attempt to run the tests if column data might be unavailable.  */
+  if (line_end > LINE_MAP_MAX_LOCATION_WITH_COLS)
+    return;
+
+  ASSERT_STREQ (tmp.get_filename (), LOCATION_FILE (line_end));
+  ASSERT_EQ (1, LOCATION_LINE (line_end));
+  ASSERT_EQ (line_bytes, LOCATION_COLUMN (line_end));
+
+  char_span lspan = location_get_source_line (tmp.get_filename (), 1);
+  ASSERT_EQ (line_display_cols,
+	     cpp_display_width (lspan.get_buffer (), lspan.length ()));
+  ASSERT_EQ (line_display_cols,
+	     location_compute_display_column (expand_location (line_end)));
+  ASSERT_EQ (0, memcmp (lspan.get_buffer () + (emoji_col - 1),
+			"\xf0\x9f\x98\x82\xf0\x9f\x98\x82", 8));
+
+  /* (caret_byte, max_width, expected_x_offset_display, [left_margin])  */
+
+  /* No constraint on the width -> no offset.  */
+  test_offset_impl (emoji_col, 0, 0);
+
+  /* Caret is before the beginning -> no offset.  */
+  test_offset_impl (0, 100, 0);
+
+  /* Caret is past the end of the line -> no offset.  */
+  test_offset_impl (line_bytes+1, 100, 0);
+
+  /* Line fits in the display -> no offset.  */
+  test_offset_impl (line_bytes, line_display_cols + test_left_margin, 0);
+  test_offset_impl (emoji_col, line_display_cols + test_left_margin, 0);
+
+  /* Line is too long for the display but caret location is OK
+     anyway -> no offset.  */
+  static const int small_width = 24;
+  test_offset_impl (1, small_width, 0);
+
+  /* Width constraint is very small -> no offset.  */
+  test_offset_impl (emoji_col, CARET_LINE_MARGIN, 0);
+
+  /* Line would be offset, but due to large line numbers, offsetting
+     would remove the whole line -> no offset.  */
+  static const int huge_left_margin = 100;
+  test_offset_impl (emoji_col, huge_left_margin, 0, huge_left_margin);
+
+  /* Line is the same length as the display, but the line number makes it too
+     long, so offset is required.  Caret is at the end so padding on the right
+     is not in effect.  */
+  for (int excess = 1; excess <= 3; ++excess)
+    test_offset_impl (line_bytes, line_display_cols + test_left_margin - excess,
+		      excess);
+
+  /* Line is much too long for the display, caret is near the end ->
+     offset should be such that the line fits in the display and caret
+     remains the same distance from the end that it was.  */
+  for (int caret_offset = 0, max_offset = MIN (CARET_LINE_MARGIN, 10);
+       caret_offset <= max_offset; ++caret_offset)
+    test_offset_impl (line_bytes - caret_offset, small_width,
+		      line_display_cols + test_left_margin - small_width);
+
+  /* As previous case but caret is closer to the middle; now we want it to end
+     up CARET_LINE_MARGIN bytes from the end.  */
+  ASSERT_GT (line_display_cols - emoji_col, CARET_LINE_MARGIN);
+  test_offset_impl (emoji_col, small_width,
+		    emoji_col + test_left_margin
+		    - (small_width - CARET_LINE_MARGIN));
+
+  /* Test that the source line is offset as expected when printed.  */
+  {
+    test_diagnostic_context dc;
+    dc.caret_max_width = small_width - 6;
+    dc.min_margin_width = test_left_margin - test_linenum_sep + 1;
+    dc.show_line_numbers_p = true;
+    dc.show_ruler_p = true;
+    rich_location richloc (line_table,
+			   linemap_position_for_column (line_table,
+							emoji_col));
+    layout test_layout (&dc, &richloc, DK_ERROR);
+    test_layout.print_line (1);
+    ASSERT_STREQ ("     |         1         \n"
+		  "     |         1         \n"
+		  "     | 234567890123456789\n"
+		  "   1 | \xf0\x9f\x98\x82\xf0\x9f\x98\x82 is a pair of emojis "
+		  "that occupies 8 bytes and 4 display columns, starting at "
+		  "column #102.\n"
+		  "     | ^\n\n",
+		  pp_formatted_text (dc.printer));
+  }
+
+  /* Similar to the previous example, but now the offset called for would split
+     the first emoji in the middle of the UTF-8 sequence.  Check that we replace
+     it with a padding space in this case.  */
+  {
+    test_diagnostic_context dc;
+    dc.caret_max_width = small_width - 5;
+    dc.min_margin_width = test_left_margin - test_linenum_sep + 1;
+    dc.show_line_numbers_p = true;
+    dc.show_ruler_p = true;
+    rich_location richloc (line_table,
+			   linemap_position_for_column (line_table,
+							emoji_col + 2));
+    layout test_layout (&dc, &richloc, DK_ERROR);
+    test_layout.print_line (1);
+    ASSERT_STREQ ("     |        1         1 \n"
+		  "     |        1         2 \n"
+		  "     | 3456789012345678901\n"
+		  "   1 |  \xf0\x9f\x98\x82 is a pair of emojis "
+		  "that occupies 8 bytes and 4 display columns, starting at "
+		  "column #102.\n"
+		  "     |  ^\n\n",
+		  pp_formatted_text (dc.printer));
+  }
+
+}
+
 /* Verify that diagnostic_show_locus works sanely on UNKNOWN_LOCATION.  */
 
 static void
@@ -2965,6 +3384,551 @@ test_diagnostic_show_locus_one_liner (const line_table_case &case_)
   test_one_liner_labels ();
 }
 
+/* Version of all one-liner tests exercising multibyte awareness.  For
+   simplicity we stick to using two multibyte characters in the test, U+1F602
+   == "\xf0\x9f\x98\x82", which uses 4 bytes and 2 display columns, and U+03C0
+   == "\xcf\x80", which uses 2 bytes and 1 display column.  Note: all of the
+   below asserts would be easier to read if we used UTF-8 directly in the
+   string constants, but it seems better not to demand the host compiler
+   support this, when it isn't otherwise necessary.  Instead, whenever an
+   extended character appears in a string, we put a line break after it so that
+   all succeeding characters can appear visually at the correct display column.
+
+   All of these work on the following 1-line source file:
+
+     .0000000001111111111222222   display
+     .1234567890123456789012345   columns
+     "SS_foo = P_bar.SS_fieldP;\n"
+     .0000000111111111222222223   byte
+     .1356789012456789134567891   columns
+
+   which is set up by test_diagnostic_show_locus_one_liner and calls
+   them.  Here SS represents the two display columns for the U+1F602 emoji and
+   P represents the one display column for the U+03C0 pi symbol.  */
+
+/* Just a caret.  */
+
+static void
+test_one_liner_simple_caret_utf8 ()
+{
+  test_diagnostic_context dc;
+  location_t caret = linemap_position_for_column (line_table, 18);
+  rich_location richloc (line_table, caret);
+  diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+  ASSERT_STREQ ("\n"
+		" \xf0\x9f\x98\x82"
+		   "_foo = \xcf\x80"
+			   "_bar.\xf0\x9f\x98\x82"
+				  "_field\xcf\x80"
+					 ";\n"
+		"               ^\n",
+		pp_formatted_text (dc.printer));
+}
+
+/* Caret and range.  */
+static void
+test_one_liner_caret_and_range_utf8 ()
+{
+  test_diagnostic_context dc;
+  location_t caret = linemap_position_for_column (line_table, 18);
+  location_t start = linemap_position_for_column (line_table, 12);
+  location_t finish = linemap_position_for_column (line_table, 30);
+  location_t loc = make_location (caret, start, finish);
+  rich_location richloc (line_table, loc);
+  diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+  ASSERT_STREQ ("\n"
+		" \xf0\x9f\x98\x82"
+		   "_foo = \xcf\x80"
+			   "_bar.\xf0\x9f\x98\x82"
+				  "_field\xcf\x80"
+					 ";\n"
+		"          ~~~~~^~~~~~~~~~\n",
+		pp_formatted_text (dc.printer));
+}
+
+/* Multiple ranges and carets.  */
+
+static void
+test_one_liner_multiple_carets_and_ranges_utf8 ()
+{
+  test_diagnostic_context dc;
+  location_t foo
+    = make_location (linemap_position_for_column (line_table, 7),
+		     linemap_position_for_column (line_table, 1),
+		     linemap_position_for_column (line_table, 8));
+  dc.caret_chars[0] = 'A';
+
+  location_t bar
+    = make_location (linemap_position_for_column (line_table, 16),
+		     linemap_position_for_column (line_table, 12),
+		     linemap_position_for_column (line_table, 17));
+  dc.caret_chars[1] = 'B';
+
+  location_t field
+    = make_location (linemap_position_for_column (line_table, 26),
+		     linemap_position_for_column (line_table, 19),
+		     linemap_position_for_column (line_table, 30));
+  dc.caret_chars[2] = 'C';
+  rich_location richloc (line_table, foo);
+  richloc.add_range (bar, SHOW_RANGE_WITH_CARET);
+  richloc.add_range (field, SHOW_RANGE_WITH_CARET);
+  diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+  ASSERT_STREQ ("\n"
+		" \xf0\x9f\x98\x82"
+		   "_foo = \xcf\x80"
+			   "_bar.\xf0\x9f\x98\x82"
+				  "_field\xcf\x80"
+					 ";\n"
+		" ~~~~A~   ~~~B~ ~~~~~C~~~\n",
+		pp_formatted_text (dc.printer));
+}
+
+/* Insertion fix-it hint: adding an "&" to the front of "P_bar.field". */
+
+static void
+test_one_liner_fixit_insert_before_utf8 ()
+{
+  test_diagnostic_context dc;
+  location_t caret = linemap_position_for_column (line_table, 12);
+  rich_location richloc (line_table, caret);
+  richloc.add_fixit_insert_before ("&");
+  diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+  ASSERT_STREQ ("\n"
+		" \xf0\x9f\x98\x82"
+		   "_foo = \xcf\x80"
+			   "_bar.\xf0\x9f\x98\x82"
+				  "_field\xcf\x80"
+					 ";\n"
+		"          ^\n"
+		"          &\n",
+		pp_formatted_text (dc.printer));
+}
+
+/* Insertion fix-it hint: adding a "[0]" after "SS_foo". */
+
+static void
+test_one_liner_fixit_insert_after_utf8 ()
+{
+  test_diagnostic_context dc;
+  location_t start = linemap_position_for_column (line_table, 1);
+  location_t finish = linemap_position_for_column (line_table, 8);
+  location_t foo = make_location (start, start, finish);
+  rich_location richloc (line_table, foo);
+  richloc.add_fixit_insert_after ("[0]");
+  diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+  ASSERT_STREQ ("\n"
+		" \xf0\x9f\x98\x82"
+		   "_foo = \xcf\x80"
+			   "_bar.\xf0\x9f\x98\x82"
+				  "_field\xcf\x80"
+					 ";\n"
+		" ^~~~~~\n"
+		"       [0]\n",
+		pp_formatted_text (dc.printer));
+}
+
+/* Removal fix-it hint: removal of the ".SS_fieldP". */
+
+static void
+test_one_liner_fixit_remove_utf8 ()
+{
+  test_diagnostic_context dc;
+  location_t start = linemap_position_for_column (line_table, 18);
+  location_t finish = linemap_position_for_column (line_table, 30);
+  location_t dot = make_location (start, start, finish);
+  rich_location richloc (line_table, dot);
+  richloc.add_fixit_remove ();
+  diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+  ASSERT_STREQ ("\n"
+		" \xf0\x9f\x98\x82"
+		   "_foo = \xcf\x80"
+			   "_bar.\xf0\x9f\x98\x82"
+				  "_field\xcf\x80"
+					 ";\n"
+		"               ^~~~~~~~~~\n"
+		"               ----------\n",
+		pp_formatted_text (dc.printer));
+}
+
+/* Replace fix-it hint: replacing "SS_fieldP" with "m_SSfieldP". */
+
+static void
+test_one_liner_fixit_replace_utf8 ()
+{
+  test_diagnostic_context dc;
+  location_t start = linemap_position_for_column (line_table, 19);
+  location_t finish = linemap_position_for_column (line_table, 30);
+  location_t field = make_location (start, start, finish);
+  rich_location richloc (line_table, field);
+  richloc.add_fixit_replace ("m_\xf0\x9f\x98\x82_field\xcf\x80");
+  diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+  ASSERT_STREQ ("\n"
+		" \xf0\x9f\x98\x82"
+		   "_foo = \xcf\x80"
+			   "_bar.\xf0\x9f\x98\x82"
+				  "_field\xcf\x80"
+					 ";\n"
+		"                ^~~~~~~~~\n"
+		"                m_\xf0\x9f\x98\x82"
+				    "_field\xcf\x80\n",
+		pp_formatted_text (dc.printer));
+}
+
+/* Replace fix-it hint: replacing "SS_fieldP" with "m_SSfieldP",
+   but where the caret was elsewhere.  */
+
+static void
+test_one_liner_fixit_replace_non_equal_range_utf8 ()
+{
+  test_diagnostic_context dc;
+  location_t equals = linemap_position_for_column (line_table, 10);
+  location_t start = linemap_position_for_column (line_table, 19);
+  location_t finish = linemap_position_for_column (line_table, 30);
+  rich_location richloc (line_table, equals);
+  source_range range;
+  range.m_start = start;
+  range.m_finish = finish;
+  richloc.add_fixit_replace (range, "m_\xf0\x9f\x98\x82_field\xcf\x80");
+  diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+  /* The replacement range is not indicated in the annotation line, so
+     it should be indicated via an additional underline.  */
+  ASSERT_STREQ ("\n"
+		" \xf0\x9f\x98\x82"
+		   "_foo = \xcf\x80"
+			   "_bar.\xf0\x9f\x98\x82"
+				  "_field\xcf\x80"
+					 ";\n"
+		"        ^\n"
+		"                ---------\n"
+		"                m_\xf0\x9f\x98\x82"
+				    "_field\xcf\x80\n",
+		pp_formatted_text (dc.printer));
+}
+
+/* Replace fix-it hint: replacing "SS_fieldP" with "m_SSfieldP",
+   where the caret was elsewhere, but where a secondary range
+   exactly covers "field".  */
+
+static void
+test_one_liner_fixit_replace_equal_secondary_range_utf8 ()
+{
+  test_diagnostic_context dc;
+  location_t equals = linemap_position_for_column (line_table, 10);
+  location_t start = linemap_position_for_column (line_table, 19);
+  location_t finish = linemap_position_for_column (line_table, 30);
+  rich_location richloc (line_table, equals);
+  location_t field = make_location (start, start, finish);
+  richloc.add_range (field);
+  richloc.add_fixit_replace (field, "m_\xf0\x9f\x98\x82_field\xcf\x80");
+  diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+  /* The replacement range is indicated in the annotation line,
+     so it shouldn't be indicated via an additional underline.  */
+  ASSERT_STREQ ("\n"
+		" \xf0\x9f\x98\x82"
+		   "_foo = \xcf\x80"
+			   "_bar.\xf0\x9f\x98\x82"
+				  "_field\xcf\x80"
+					 ";\n"
+		"        ^       ~~~~~~~~~\n"
+		"                m_\xf0\x9f\x98\x82"
+				    "_field\xcf\x80\n",
+		pp_formatted_text (dc.printer));
+}
+
+/* Verify that we can use ad-hoc locations when adding fixits to a
+   rich_location.  */
+
+static void
+test_one_liner_fixit_validation_adhoc_locations_utf8 ()
+{
+  /* Generate a range that's too long to be packed, so must
+     be stored as an ad-hoc location (given the defaults
+     of 5 bits or 0 bits of packed range); 41 columns > 2**5.  */
+  const location_t c12 = linemap_position_for_column (line_table, 12);
+  const location_t c52 = linemap_position_for_column (line_table, 52);
+  const location_t loc = make_location (c12, c12, c52);
+
+  if (c52 > LINE_MAP_MAX_LOCATION_WITH_COLS)
+    return;
+
+  ASSERT_TRUE (IS_ADHOC_LOC (loc));
+
+  /* Insert.  */
+  {
+    rich_location richloc (line_table, loc);
+    richloc.add_fixit_insert_before (loc, "test");
+    /* It should not have been discarded by the validator.  */
+    ASSERT_EQ (1, richloc.get_num_fixit_hints ());
+
+    test_diagnostic_context dc;
+    diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+    ASSERT_STREQ ("\n"
+		  " \xf0\x9f\x98\x82"
+		     "_foo = \xcf\x80"
+			     "_bar.\xf0\x9f\x98\x82"
+				    "_field\xcf\x80"
+					   ";\n"
+		  "          ^~~~~~~~~~~~~~~~                     \n"
+		  "          test\n",
+		pp_formatted_text (dc.printer));
+  }
+
+  /* Remove.  */
+  {
+    rich_location richloc (line_table, loc);
+    source_range range = source_range::from_locations (loc, c52);
+    richloc.add_fixit_remove (range);
+    /* It should not have been discarded by the validator.  */
+    ASSERT_EQ (1, richloc.get_num_fixit_hints ());
+
+    test_diagnostic_context dc;
+    diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+    ASSERT_STREQ ("\n"
+		  " \xf0\x9f\x98\x82"
+		     "_foo = \xcf\x80"
+			     "_bar.\xf0\x9f\x98\x82"
+				    "_field\xcf\x80"
+					   ";\n"
+		  "          ^~~~~~~~~~~~~~~~                     \n"
+		  "          -------------------------------------\n",
+		pp_formatted_text (dc.printer));
+  }
+
+  /* Replace.  */
+  {
+    rich_location richloc (line_table, loc);
+    source_range range = source_range::from_locations (loc, c52);
+    richloc.add_fixit_replace (range, "test");
+    /* It should not have been discarded by the validator.  */
+    ASSERT_EQ (1, richloc.get_num_fixit_hints ());
+
+    test_diagnostic_context dc;
+    diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+    ASSERT_STREQ ("\n"
+		  " \xf0\x9f\x98\x82"
+		     "_foo = \xcf\x80"
+			     "_bar.\xf0\x9f\x98\x82"
+				    "_field\xcf\x80"
+					   ";\n"
+		  "          ^~~~~~~~~~~~~~~~                     \n"
+		  "          test\n",
+		pp_formatted_text (dc.printer));
+  }
+}
+
+/* Test of consolidating insertions at the same location.  */
+
+static void
+test_one_liner_many_fixits_1_utf8 ()
+{
+  test_diagnostic_context dc;
+  location_t equals = linemap_position_for_column (line_table, 10);
+  rich_location richloc (line_table, equals);
+  for (int i = 0; i < 19; i++)
+    richloc.add_fixit_insert_before (i & 1 ? "@" : "\xcf\x80");
+  ASSERT_EQ (1, richloc.get_num_fixit_hints ());
+  diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+  ASSERT_STREQ ("\n"
+		" \xf0\x9f\x98\x82"
+		   "_foo = \xcf\x80"
+			   "_bar.\xf0\x9f\x98\x82"
+				  "_field\xcf\x80"
+					 ";\n"
+		"        ^\n"
+		"        \xcf\x80@\xcf\x80@\xcf\x80@\xcf\x80@\xcf\x80@"
+		"\xcf\x80@\xcf\x80@\xcf\x80@\xcf\x80@\xcf\x80\n",
+		pp_formatted_text (dc.printer));
+}
+
+/* Ensure that we can add an arbitrary number of fix-it hints to a
+   rich_location, even if they are not consolidated.  */
+
+static void
+test_one_liner_many_fixits_2_utf8 ()
+{
+  test_diagnostic_context dc;
+  location_t equals = linemap_position_for_column (line_table, 10);
+  rich_location richloc (line_table, equals);
+  const int nlocs = 19;
+  int locs[nlocs] = {1, 5, 7, 9, 11, 14, 16, 18, 23, 25, 27, 29, 32,
+		     34, 36, 38, 40, 42, 44};
+  for (int i = 0; i != nlocs; ++i)
+    {
+      location_t loc = linemap_position_for_column (line_table, locs[i]);
+      richloc.add_fixit_insert_before (loc, i & 1 ? "@" : "\xcf\x80");
+    }
+
+  ASSERT_EQ (nlocs, richloc.get_num_fixit_hints ());
+  diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+  ASSERT_STREQ ("\n"
+		" \xf0\x9f\x98\x82"
+		   "_foo = \xcf\x80"
+			   "_bar.\xf0\x9f\x98\x82"
+				  "_field\xcf\x80"
+					 ";\n"
+		"        ^\n"
+		" \xcf\x80 @ \xcf\x80 @ \xcf\x80 @ \xcf\x80 @  \xcf\x80 @"
+		" \xcf\x80 @ \xcf\x80 @ \xcf\x80 @ \xcf\x80 @ \xcf\x80\n",
+		pp_formatted_text (dc.printer));
+}
+
+/* Test of labeling the ranges within a rich_location.  */
+
+static void
+test_one_liner_labels_utf8 ()
+{
+  location_t foo
+    = make_location (linemap_position_for_column (line_table, 1),
+		     linemap_position_for_column (line_table, 1),
+		     linemap_position_for_column (line_table, 8));
+  location_t bar
+    = make_location (linemap_position_for_column (line_table, 12),
+		     linemap_position_for_column (line_table, 12),
+		     linemap_position_for_column (line_table, 17));
+  location_t field
+    = make_location (linemap_position_for_column (line_table, 19),
+		     linemap_position_for_column (line_table, 19),
+		     linemap_position_for_column (line_table, 30));
+
+  /* Example where all the labels fit on one line.  */
+  {
+    /* These three labels contain multibyte characters such that their byte
+       lengths are respectively (12, 10, 18), but their display widths are only
+       (6, 5, 9).  All three fit on the line when considering the display
+       widths, but not when considering the byte widths, so verify that we do
+       indeed put them all on one line.  */
+    text_range_label label0
+      ("\xcf\x80\xcf\x80\xcf\x80\xcf\x80\xcf\x80\xcf\x80");
+    text_range_label label1
+      ("\xf0\x9f\x98\x82\xf0\x9f\x98\x82\xcf\x80");
+    text_range_label label2
+      ("\xf0\x9f\x98\x82\xcf\x80\xf0\x9f\x98\x82\xf0\x9f\x98\x82\xcf\x80"
+       "\xcf\x80");
+    gcc_rich_location richloc (foo, &label0);
+    richloc.add_range (bar, SHOW_RANGE_WITHOUT_CARET, &label1);
+    richloc.add_range (field, SHOW_RANGE_WITHOUT_CARET, &label2);
+
+    {
+      test_diagnostic_context dc;
+      diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+      ASSERT_STREQ ("\n"
+		    " \xf0\x9f\x98\x82"
+		       "_foo = \xcf\x80"
+			       "_bar.\xf0\x9f\x98\x82"
+				      "_field\xcf\x80"
+					     ";\n"
+		    " ^~~~~~   ~~~~~ ~~~~~~~~~\n"
+		    " |        |     |\n"
+		    " \xcf\x80\xcf\x80\xcf\x80\xcf\x80\xcf\x80\xcf\x80"
+			   "   \xf0\x9f\x98\x82\xf0\x9f\x98\x82\xcf\x80"
+				   " \xf0\x9f\x98\x82\xcf\x80\xf0\x9f\x98\x82"
+					 "\xf0\x9f\x98\x82\xcf\x80\xcf\x80\n",
+		    pp_formatted_text (dc.printer));
+    }
+
+  }
+
+  /* Example where the labels need extra lines.  */
+  {
+    text_range_label label0 ("label 0\xf0\x9f\x98\x82");
+    text_range_label label1 ("label 1\xcf\x80");
+    text_range_label label2 ("label 2\xcf\x80");
+    gcc_rich_location richloc (foo, &label0);
+    richloc.add_range (bar, SHOW_RANGE_WITHOUT_CARET, &label1);
+    richloc.add_range (field, SHOW_RANGE_WITHOUT_CARET, &label2);
+
+    test_diagnostic_context dc;
+    diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+
+    ASSERT_STREQ ("\n"
+		  " \xf0\x9f\x98\x82"
+		     "_foo = \xcf\x80"
+			     "_bar.\xf0\x9f\x98\x82"
+				    "_field\xcf\x80"
+					   ";\n"
+		  " ^~~~~~   ~~~~~ ~~~~~~~~~\n"
+		  " |        |     |\n"
+		  " |        |     label 2\xcf\x80\n"
+		  " |        label 1\xcf\x80\n"
+		  " label 0\xf0\x9f\x98\x82\n",
+		  pp_formatted_text (dc.printer));
+  }
+
+  /* Example of boundary conditions: label 0 and 1 have just enough clearance,
+     but label 1 just touches label 2.  */
+  {
+    text_range_label label0 ("aaaaa\xf0\x9f\x98\x82\xcf\x80");
+    text_range_label label1 ("bb\xf0\x9f\x98\x82\xf0\x9f\x98\x82");
+    text_range_label label2 ("c");
+    gcc_rich_location richloc (foo, &label0);
+    richloc.add_range (bar, SHOW_RANGE_WITHOUT_CARET, &label1);
+    richloc.add_range (field, SHOW_RANGE_WITHOUT_CARET, &label2);
+
+    test_diagnostic_context dc;
+    diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+    ASSERT_STREQ ("\n"
+		  " \xf0\x9f\x98\x82"
+		     "_foo = \xcf\x80"
+			     "_bar.\xf0\x9f\x98\x82"
+				    "_field\xcf\x80"
+					   ";\n"
+		  " ^~~~~~   ~~~~~ ~~~~~~~~~\n"
+		  " |        |     |\n"
+		  " |        |     c\n"
+		  " aaaaa\xf0\x9f\x98\x82\xcf\x80"
+			   " bb\xf0\x9f\x98\x82\xf0\x9f\x98\x82\n",
+		  pp_formatted_text (dc.printer));
+  }
+}
+
+/* Run the various one-liner tests.  */
+
+static void
+test_diagnostic_show_locus_one_liner_utf8 (const line_table_case &case_)
+{
+  /* Create a tempfile and write some text to it.  */
+  const char *content
+    /* Display columns.
+       0000000000000000000000011111111111111111111111111111112222222222222
+       1111111122222222345678900000000123456666666677777777890123444444445  */
+    = "\xf0\x9f\x98\x82_foo = \xcf\x80_bar.\xf0\x9f\x98\x82_field\xcf\x80;\n";
+    /* 0000000000000000000001111111111111111111222222222222222222222233333
+       1111222233334444567890122223333456789999000011112222345678999900001
+       Byte columns.  */
+  temp_source_file tmp (SELFTEST_LOCATION, ".c", content);
+  line_table_test ltt (case_);
+
+  linemap_add (line_table, LC_ENTER, false, tmp.get_filename (), 1);
+
+  location_t line_end = linemap_position_for_column (line_table, 31);
+
+  /* Don't attempt to run the tests if column data might be unavailable.  */
+  if (line_end > LINE_MAP_MAX_LOCATION_WITH_COLS)
+    return;
+
+  ASSERT_STREQ (tmp.get_filename (), LOCATION_FILE (line_end));
+  ASSERT_EQ (1, LOCATION_LINE (line_end));
+  ASSERT_EQ (31, LOCATION_COLUMN (line_end));
+
+  char_span lspan = location_get_source_line (tmp.get_filename (), 1);
+  ASSERT_EQ (25, cpp_display_width (lspan.get_buffer (), lspan.length ()));
+  ASSERT_EQ (25, location_compute_display_column (expand_location (line_end)));
+
+  test_one_liner_simple_caret_utf8 ();
+  test_one_liner_caret_and_range_utf8 ();
+  test_one_liner_multiple_carets_and_ranges_utf8 ();
+  test_one_liner_fixit_insert_before_utf8 ();
+  test_one_liner_fixit_insert_after_utf8 ();
+  test_one_liner_fixit_remove_utf8 ();
+  test_one_liner_fixit_replace_utf8 ();
+  test_one_liner_fixit_replace_non_equal_range_utf8 ();
+  test_one_liner_fixit_replace_equal_secondary_range_utf8 ();
+  test_one_liner_fixit_validation_adhoc_locations_utf8 ();
+  test_one_liner_many_fixits_1_utf8 ();
+  test_one_liner_many_fixits_2_utf8 ();
+  test_one_liner_labels_utf8 ();
+}
+
 /* Verify that gcc_rich_location::add_location_if_nearby works.  */
 
 static void
@@ -3340,13 +4304,19 @@ test_overlapped_fixit_printing (const line_table_case &case_)
     /* Unit-test the line_corrections machinery.  */
     ASSERT_EQ (3, richloc.get_num_fixit_hints ());
     const fixit_hint *hint_0 = richloc.get_fixit_hint (0);
-    ASSERT_EQ (column_range (12, 12), get_affected_columns (hint_0));
+    ASSERT_EQ (column_range (12, 12), get_affected_range (hint_0, CU_BYTES));
+    ASSERT_EQ (column_range (12, 12),
+			   get_affected_range (hint_0, CU_DISPLAY_COLS));
     ASSERT_EQ (column_range (12, 22), get_printed_columns (hint_0));
     const fixit_hint *hint_1 = richloc.get_fixit_hint (1);
-    ASSERT_EQ (column_range (18, 18), get_affected_columns (hint_1));
+    ASSERT_EQ (column_range (18, 18), get_affected_range (hint_1, CU_BYTES));
+    ASSERT_EQ (column_range (18, 18),
+			   get_affected_range (hint_1, CU_DISPLAY_COLS));
     ASSERT_EQ (column_range (18, 20), get_printed_columns (hint_1));
     const fixit_hint *hint_2 = richloc.get_fixit_hint (2);
-    ASSERT_EQ (column_range (29, 28), get_affected_columns (hint_2));
+    ASSERT_EQ (column_range (29, 28), get_affected_range (hint_2, CU_BYTES));
+    ASSERT_EQ (column_range (29, 28),
+			   get_affected_range (hint_2, CU_DISPLAY_COLS));
     ASSERT_EQ (column_range (29, 29), get_printed_columns (hint_2));
 
     /* Add each hint in turn to a line_corrections instance,
@@ -3357,6 +4327,7 @@ test_overlapped_fixit_printing (const line_table_case &case_)
     /* The first replace hint by itself.  */
     lc.add_hint (hint_0);
     ASSERT_EQ (1, lc.m_corrections.length ());
+    ASSERT_EQ (column_range (12, 12), lc.m_corrections[0]->m_affected_bytes);
     ASSERT_EQ (column_range (12, 12), lc.m_corrections[0]->m_affected_columns);
     ASSERT_EQ (column_range (12, 22), lc.m_corrections[0]->m_printed_columns);
     ASSERT_STREQ ("const_cast<", lc.m_corrections[0]->m_text);
@@ -3366,6 +4337,7 @@ test_overlapped_fixit_printing (const line_table_case &case_)
     lc.add_hint (hint_1);
     ASSERT_EQ (1, lc.m_corrections.length ());
     ASSERT_STREQ ("const_cast<foo *> (", lc.m_corrections[0]->m_text);
+    ASSERT_EQ (column_range (12, 18), lc.m_corrections[0]->m_affected_bytes);
     ASSERT_EQ (column_range (12, 18), lc.m_corrections[0]->m_affected_columns);
     ASSERT_EQ (column_range (12, 30), lc.m_corrections[0]->m_printed_columns);
 
@@ -3375,6 +4347,7 @@ test_overlapped_fixit_printing (const line_table_case &case_)
     ASSERT_STREQ ("const_cast<foo *> (ptr->field)",
 		  lc.m_corrections[0]->m_text);
     ASSERT_EQ (1, lc.m_corrections.length ());
+    ASSERT_EQ (column_range (12, 28), lc.m_corrections[0]->m_affected_bytes);
     ASSERT_EQ (column_range (12, 28), lc.m_corrections[0]->m_affected_columns);
     ASSERT_EQ (column_range (12, 41), lc.m_corrections[0]->m_printed_columns);
   }
@@ -3477,6 +4450,246 @@ test_overlapped_fixit_printing (const line_table_case &case_)
   }
 }
 
+/* Multibyte-aware version of preceding tests.  See comments above
+   test_one_liner_simple_caret_utf8() too, we use the same two multibyte
+   characters here.  */
+
+static void
+test_overlapped_fixit_printing_utf8 (const line_table_case &case_)
+{
+  /* Create a tempfile and write some text to it.  */
+
+  const char *content
+    /* Display columns.
+       00000000000000000000000111111111111111111111111222222222222222223
+       12344444444555555556789012344444444555555556789012345678999999990  */
+    = "  f\xf0\x9f\x98\x82 *f = (f\xf0\x9f\x98\x82 *)ptr->field\xcf\x80;\n";
+    /* 00000000000000000000011111111111111111111112222222222333333333333
+       12344445555666677778901234566667777888899990123456789012333344445
+       Byte columns.  */
+
+  temp_source_file tmp (SELFTEST_LOCATION, ".C", content);
+  line_table_test ltt (case_);
+
+  const line_map_ordinary *ord_map
+    = linemap_check_ordinary (linemap_add (line_table, LC_ENTER, false,
+					   tmp.get_filename (), 0));
+
+  linemap_line_start (line_table, 1, 100);
+
+  const location_t final_line_end
+    = linemap_position_for_line_and_column (line_table, ord_map, 6, 50);
+
+  /* Don't attempt to run the tests if column data might be unavailable.  */
+  if (final_line_end > LINE_MAP_MAX_LOCATION_WITH_COLS)
+    return;
+
+  /* A test for converting a C-style cast to a C++-style cast.  */
+  const location_t open_paren
+    = linemap_position_for_line_and_column (line_table, ord_map, 1, 14);
+  const location_t close_paren
+    = linemap_position_for_line_and_column (line_table, ord_map, 1, 22);
+  const location_t expr_start
+    = linemap_position_for_line_and_column (line_table, ord_map, 1, 23);
+  const location_t expr_finish
+    = linemap_position_for_line_and_column (line_table, ord_map, 1, 34);
+  const location_t expr = make_location (expr_start, expr_start, expr_finish);
+
+  /* Various examples of fix-it hints that aren't themselves consolidated,
+     but for which the *printing* may need consolidation.  */
+
+  /* Example where 3 fix-it hints are printed as one.  */
+  {
+    test_diagnostic_context dc;
+    rich_location richloc (line_table, expr);
+    richloc.add_fixit_replace (open_paren, "const_cast<");
+    richloc.add_fixit_replace (close_paren, "> (");
+    richloc.add_fixit_insert_after (")");
+
+    diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+    ASSERT_STREQ ("\n"
+		  "   f\xf0\x9f\x98\x82"
+			" *f = (f\xf0\x9f\x98\x82"
+				  " *)ptr->field\xcf\x80"
+						";\n"
+		  "                   ^~~~~~~~~~~\n"
+		  "            ------------------\n"
+		  "            const_cast<f\xf0\x9f\x98\x82"
+					    " *> (ptr->field\xcf\x80"
+							    ")\n",
+		  pp_formatted_text (dc.printer));
+
+    /* Unit-test the line_corrections machinery.  */
+    ASSERT_EQ (3, richloc.get_num_fixit_hints ());
+    const fixit_hint *hint_0 = richloc.get_fixit_hint (0);
+    ASSERT_EQ (column_range (14, 14), get_affected_range (hint_0, CU_BYTES));
+    ASSERT_EQ (column_range (12, 12),
+			   get_affected_range (hint_0, CU_DISPLAY_COLS));
+    ASSERT_EQ (column_range (12, 22), get_printed_columns (hint_0));
+    const fixit_hint *hint_1 = richloc.get_fixit_hint (1);
+    ASSERT_EQ (column_range (22, 22), get_affected_range (hint_1, CU_BYTES));
+    ASSERT_EQ (column_range (18, 18),
+			   get_affected_range (hint_1, CU_DISPLAY_COLS));
+    ASSERT_EQ (column_range (18, 20), get_printed_columns (hint_1));
+    const fixit_hint *hint_2 = richloc.get_fixit_hint (2);
+    ASSERT_EQ (column_range (35, 34), get_affected_range (hint_2, CU_BYTES));
+    ASSERT_EQ (column_range (30, 29),
+			   get_affected_range (hint_2, CU_DISPLAY_COLS));
+    ASSERT_EQ (column_range (30, 30), get_printed_columns (hint_2));
+
+    /* Add each hint in turn to a line_corrections instance,
+       and verify that they are consolidated into one correction instance
+       as expected.  */
+    line_corrections lc (tmp.get_filename (), 1);
+
+    /* The first replace hint by itself.  */
+    lc.add_hint (hint_0);
+    ASSERT_EQ (1, lc.m_corrections.length ());
+    ASSERT_EQ (column_range (14, 14), lc.m_corrections[0]->m_affected_bytes);
+    ASSERT_EQ (column_range (12, 12), lc.m_corrections[0]->m_affected_columns);
+    ASSERT_EQ (column_range (12, 22), lc.m_corrections[0]->m_printed_columns);
+    ASSERT_STREQ ("const_cast<", lc.m_corrections[0]->m_text);
+
+    /* After the second replacement hint, they are printed together
+       as a replacement (along with the text between them).  */
+    lc.add_hint (hint_1);
+    ASSERT_EQ (1, lc.m_corrections.length ());
+    ASSERT_STREQ ("const_cast<f\xf0\x9f\x98\x82 *> (",
+		  lc.m_corrections[0]->m_text);
+    ASSERT_EQ (column_range (14, 22), lc.m_corrections[0]->m_affected_bytes);
+    ASSERT_EQ (column_range (12, 18), lc.m_corrections[0]->m_affected_columns);
+    ASSERT_EQ (column_range (12, 30), lc.m_corrections[0]->m_printed_columns);
+
+    /* After the final insertion hint, they are all printed together
+       as a replacement (along with the text between them).  */
+    lc.add_hint (hint_2);
+    ASSERT_STREQ ("const_cast<f\xf0\x9f\x98\x82 *> (ptr->field\xcf\x80)",
+		  lc.m_corrections[0]->m_text);
+    ASSERT_EQ (1, lc.m_corrections.length ());
+    ASSERT_EQ (column_range (14, 34), lc.m_corrections[0]->m_affected_bytes);
+    ASSERT_EQ (column_range (12, 29), lc.m_corrections[0]->m_affected_columns);
+    ASSERT_EQ (column_range (12, 42), lc.m_corrections[0]->m_printed_columns);
+  }
+
+  /* Example where two are consolidated during printing.  */
+  {
+    test_diagnostic_context dc;
+    rich_location richloc (line_table, expr);
+    richloc.add_fixit_replace (open_paren, "CAST (");
+    richloc.add_fixit_replace (close_paren, ") (");
+    richloc.add_fixit_insert_after (")");
+
+    diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+    ASSERT_STREQ ("\n"
+		  "   f\xf0\x9f\x98\x82"
+			" *f = (f\xf0\x9f\x98\x82"
+				  " *)ptr->field\xcf\x80"
+						";\n"
+		  "                   ^~~~~~~~~~~\n"
+		  "            -\n"
+		  "            CAST (-\n"
+		  "                  ) (         )\n",
+		  pp_formatted_text (dc.printer));
+  }
+
+  /* Example where none are consolidated during printing.  */
+  {
+    test_diagnostic_context dc;
+    rich_location richloc (line_table, expr);
+    richloc.add_fixit_replace (open_paren, "CST (");
+    richloc.add_fixit_replace (close_paren, ") (");
+    richloc.add_fixit_insert_after (")");
+
+    diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+    ASSERT_STREQ ("\n"
+		  "   f\xf0\x9f\x98\x82"
+			" *f = (f\xf0\x9f\x98\x82"
+				  " *)ptr->field\xcf\x80"
+						";\n"
+		  "                   ^~~~~~~~~~~\n"
+		  "            -\n"
+		  "            CST ( -\n"
+		  "                  ) (         )\n",
+		  pp_formatted_text (dc.printer));
+  }
+
+  /* Example of deletion fix-it hints.  */
+  {
+    test_diagnostic_context dc;
+    rich_location richloc (line_table, expr);
+    richloc.add_fixit_insert_before (open_paren, "(bar\xf0\x9f\x98\x82 *)");
+    source_range victim = {open_paren, close_paren};
+    richloc.add_fixit_remove (victim);
+
+    /* This case is actually handled by fixit-consolidation,
+       rather than by line_corrections.  */
+    ASSERT_EQ (1, richloc.get_num_fixit_hints ());
+
+    diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+    ASSERT_STREQ ("\n"
+		  "   f\xf0\x9f\x98\x82"
+			" *f = (f\xf0\x9f\x98\x82"
+				  " *)ptr->field\xcf\x80"
+						";\n"
+		  "                   ^~~~~~~~~~~\n"
+		  "            -------\n"
+		  "            (bar\xf0\x9f\x98\x82"
+				    " *)\n",
+		  pp_formatted_text (dc.printer));
+  }
+
+  /* Example of deletion fix-it hints that would overlap.  */
+  {
+    test_diagnostic_context dc;
+    rich_location richloc (line_table, expr);
+    richloc.add_fixit_insert_before (open_paren, "(long\xf0\x9f\x98\x82 *)");
+    source_range victim = {expr_start, expr_finish};
+    richloc.add_fixit_remove (victim);
+
+    /* These fixits are not consolidated.  */
+    ASSERT_EQ (2, richloc.get_num_fixit_hints ());
+
+    /* But the corrections are.  */
+    diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+    ASSERT_STREQ ("\n"
+		  "   f\xf0\x9f\x98\x82"
+			" *f = (f\xf0\x9f\x98\x82"
+				  " *)ptr->field\xcf\x80"
+						";\n"
+		  "                   ^~~~~~~~~~~\n"
+		  "            ------------------\n"
+		  "            (long\xf0\x9f\x98\x82"
+				     " *)(f\xf0\x9f\x98\x82"
+					    " *)\n",
+		  pp_formatted_text (dc.printer));
+  }
+
+  /* Example of insertion fix-it hints that would overlap.  */
+  {
+    test_diagnostic_context dc;
+    rich_location richloc (line_table, expr);
+    richloc.add_fixit_insert_before
+      (open_paren, "L\xf0\x9f\x98\x82NGER THAN THE CAST");
+    richloc.add_fixit_insert_after (close_paren, "TEST");
+
+    /* The first insertion is long enough that if printed naively,
+       it would overlap with the second.
+       Verify that they are printed as a single replacement.  */
+    diagnostic_show_locus (&dc, &richloc, DK_ERROR);
+    ASSERT_STREQ ("\n"
+		  "   f\xf0\x9f\x98\x82"
+			" *f = (f\xf0\x9f\x98\x82"
+				  " *)ptr->field\xcf\x80"
+						";\n"
+		  "                   ^~~~~~~~~~~\n"
+		  "            -------\n"
+		  "            L\xf0\x9f\x98\x82"
+				 "NGER THAN THE CAST(f\xf0\x9f\x98\x82"
+						       " *)TEST\n",
+		  pp_formatted_text (dc.printer));
+  }
+}
+
 /* Verify that the line_corrections machinery correctly prints
    overlapping fixit-hints that have been added in the wrong
    order.
@@ -3526,10 +4739,10 @@ test_overlapped_fixit_printing_2 (const line_table_case &case_)
     /* These fixits should be accepted; they can't be consolidated.  */
     ASSERT_EQ (2, richloc.get_num_fixit_hints ());
     const fixit_hint *hint_0 = richloc.get_fixit_hint (0);
-    ASSERT_EQ (column_range (23, 22), get_affected_columns (hint_0));
+    ASSERT_EQ (column_range (23, 22), get_affected_range (hint_0, CU_BYTES));
     ASSERT_EQ (column_range (23, 23), get_printed_columns (hint_0));
     const fixit_hint *hint_1 = richloc.get_fixit_hint (1);
-    ASSERT_EQ (column_range (21, 20), get_affected_columns (hint_1));
+    ASSERT_EQ (column_range (21, 20), get_affected_range (hint_1, CU_BYTES));
     ASSERT_EQ (column_range (21, 21), get_printed_columns (hint_1));
 
     /* Verify that they're printed correctly.  */
@@ -3851,15 +5064,19 @@ diagnostic_show_locus_c_tests ()
   test_layout_range_for_single_line ();
   test_layout_range_for_multiple_lines ();
 
-  test_get_line_width_without_trailing_whitespace ();
+  for_each_line_table_case (test_layout_x_offset_display_utf8);
+
+  test_get_line_bytes_without_trailing_whitespace ();
 
   test_diagnostic_show_locus_unknown_location ();
 
   for_each_line_table_case (test_diagnostic_show_locus_one_liner);
+  for_each_line_table_case (test_diagnostic_show_locus_one_liner_utf8);
   for_each_line_table_case (test_add_location_if_nearby);
   for_each_line_table_case (test_diagnostic_show_locus_fixit_lines);
   for_each_line_table_case (test_fixit_consolidation);
   for_each_line_table_case (test_overlapped_fixit_printing);
+  for_each_line_table_case (test_overlapped_fixit_printing_utf8);
   for_each_line_table_case (test_overlapped_fixit_printing_2);
   for_each_line_table_case (test_fixit_insert_containing_newline);
   for_each_line_table_case (test_fixit_insert_containing_newline_2);
diff --git a/gcc/input.c b/gcc/input.c
index 00301ef..1dc6b33 100644
--- a/gcc/input.c
+++ b/gcc/input.c
@@ -908,6 +908,22 @@ make_location (location_t caret, source_range src_range)
   return COMBINE_LOCATION_DATA (line_table, pure_loc, src_range, NULL);
 }
 
+/* An expanded_location stores the column in byte units.  This function
+   converts that column to display units.  That requires reading the associated
+   source line in order to calculate the display width.  If that cannot be done
+   for any reason, then returns the byte column as a fallback.  */
+int
+location_compute_display_column (expanded_location exploc)
+{
+  if (!(exploc.file && *exploc.file && exploc.line && exploc.column))
+    return exploc.column;
+  char_span line = location_get_source_line (exploc.file, exploc.line);
+  /* If line is NULL, this function returns exploc.column which is the
+     desired fallback.  */
+  return cpp_byte_column_to_display_column (line.get_buffer (), line.length (),
+					    exploc.column);
+}
+
 /* Dump statistics to stderr about the memory usage of the line_table
    set of line maps.  This also displays some statistics about macro
    expansion.  */
@@ -3590,6 +3606,93 @@ test_line_offset_overflow ()
   ASSERT_NE (ordmap_a, ordmap_b);
 }
 
+void test_cpp_utf8 ()
+{
+  /* Verify that wcwidth of invalid UTF-8 or control bytes is 1.  */
+  {
+    int w_bad = cpp_display_width ("\xf0!\x9f!\x98!\x82!", 8);
+    ASSERT_EQ (8, w_bad);
+    int w_ctrl = cpp_display_width ("\r\t\n\v\0\1", 6);
+    ASSERT_EQ (6, w_ctrl);
+  }
+
+  /* Verify that wcwidth of valid UTF-8 is as expected.  */
+  {
+    const int w_pi = cpp_display_width ("\xcf\x80", 2);
+    ASSERT_EQ (1, w_pi);
+    const int w_emoji = cpp_display_width ("\xf0\x9f\x98\x82", 4);
+    ASSERT_EQ (2, w_emoji);
+    const int w_umlaut_precomposed = cpp_display_width ("\xc3\xbf", 2);
+    ASSERT_EQ (1, w_umlaut_precomposed);
+    const int w_umlaut_combining = cpp_display_width ("y\xcc\x88", 3);
+    ASSERT_EQ (1, w_umlaut_combining);
+    const int w_han = cpp_display_width ("\xe4\xb8\xba", 3);
+    ASSERT_EQ (2, w_han);
+    const int w_ascii = cpp_display_width ("GCC", 3);
+    ASSERT_EQ (3, w_ascii);
+    const int w_mixed = cpp_display_width ("\xcf\x80 = 3.14 \xf0\x9f\x98\x82"
+					   "\x9f! \xe4\xb8\xba y\xcc\x88", 24);
+    ASSERT_EQ (18, w_mixed);
+  }
+
+  /* Verify that cpp_byte_column_to_display_column can go past the end,
+     and similar edge cases.  */
+  {
+    const char *str
+      /* Display columns.
+         111111112345  */
+      = "\xcf\x80 abc";
+      /* 111122223456
+	 Byte columns.  */
+
+    ASSERT_EQ (5, cpp_display_width (str, 6));
+    ASSERT_EQ (105, cpp_byte_column_to_display_column (str, 6, 106));
+    ASSERT_EQ (10000, cpp_byte_column_to_display_column (NULL, 0, 10000));
+    ASSERT_EQ (0, cpp_byte_column_to_display_column (NULL, 10000, 0));
+  }
+
+  /* Verify that cpp_display_column_to_byte_column can go past the end,
+     and similar edge cases, and check invertibility.  */
+  {
+    const char *str
+      /* Display columns.
+	 000000000000000000000000000000000000011
+	 111111112222222234444444455555555678901  */
+      = "\xf0\x9f\x98\x82 \xf0\x9f\x98\x82 hello";
+      /* 000000000000000000000000000000000111111
+	 111122223333444456666777788889999012345
+	 Byte columns.  */
+    ASSERT_EQ (4, cpp_display_column_to_byte_column (str, 15, 2));
+    ASSERT_EQ (15, cpp_display_column_to_byte_column (str, 15, 11));
+    ASSERT_EQ (115, cpp_display_column_to_byte_column (str, 15, 111));
+    ASSERT_EQ (10000, cpp_display_column_to_byte_column (NULL, 0, 10000));
+    ASSERT_EQ (0, cpp_display_column_to_byte_column (NULL, 10000, 0));
+
+    /* Verify that we do not interrupt a UTF-8 sequence.  */
+    ASSERT_EQ (4, cpp_display_column_to_byte_column (str, 15, 1));
+
+    for (int byte_col = 1; byte_col <= 15; ++byte_col)
+      {
+	const int disp_col = cpp_byte_column_to_display_column (str, 15,
+								byte_col);
+	const int byte_col2 = cpp_display_column_to_byte_column (str, 15,
+								 disp_col);
+
+	/* If we ask for the display column in the middle of a UTF-8
+	   sequence, it will return the length of the partial sequence,
+	   matching the behavior of GCC before display column support.
+	   Otherwise check the round trip was successful.  */
+	if (byte_col < 4)
+	  ASSERT_EQ (byte_col, disp_col);
+	else if (byte_col >= 6 && byte_col < 9)
+	  ASSERT_EQ (3 + (byte_col - 5), disp_col);
+	else
+	  ASSERT_EQ (byte_col2, byte_col);
+      }
+  }
+
+}
+
 /* Run all of the selftests within this file.  */
 
 void
@@ -3631,6 +3734,8 @@ input_c_tests ()
   test_reading_source_line ();
 
   test_line_offset_overflow ();
+
+  test_cpp_utf8 ();
 }
 
 } // namespace selftest
diff --git a/gcc/input.h b/gcc/input.h
index c459bf2..35e02bd 100644
--- a/gcc/input.h
+++ b/gcc/input.h
@@ -38,6 +38,7 @@ STATIC_ASSERT (BUILTINS_LOCATION < RESERVED_LOCATION_COUNT);
 
 extern bool is_location_from_builtin_token (location_t);
 extern expanded_location expand_location (location_t);
+extern int location_compute_display_column (expanded_location);
 
 /* A class capturing the bounds of a buffer, to allow for run-time
    bounds-checking in a checked build.  */
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 088718e..a034070 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,11 @@
+2019-12-09  Lewis Hyatt  <lhyatt@gmail.com>
+
+	PR preprocessor/49973
+	* gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
+	(test_show_locus): Tweak so that expected output is the same as
+	before the diagnostic-show-locus.c changes.
+	* gcc.dg/cpp/pr66415-1.c: Likewise.
+
 2019-12-09  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gnat.dg/lto23.adb: New test.
diff --git a/gcc/testsuite/gcc.dg/cpp/pr66415-1.c b/gcc/testsuite/gcc.dg/cpp/pr66415-1.c
index cc4e417..4a0ef55 100644
--- a/gcc/testsuite/gcc.dg/cpp/pr66415-1.c
+++ b/gcc/testsuite/gcc.dg/cpp/pr66415-1.c
@@ -1,7 +1,7 @@
 /* PR c/66415 */
 /* { dg-do compile } */
 /* { dg-options "-Wformat -fdiagnostics-show-caret" } */
-/* { dg-set-compiler-env-var COLUMNS "82" } */
+/* { dg-set-compiler-env-var COLUMNS "83" } */
 
 void
 fn1 (void)
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_show_locus.c b/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
index 3f62edd..153bdb2 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
@@ -174,7 +174,7 @@ test_show_locus (function *fun)
 
   /* Hardcode the "terminal width", to verify the behavior of
      very wide lines.  */
-  global_dc->caret_max_width = 70;
+  global_dc->caret_max_width = 71;
 
   if (0 == strcmp (fnname, "test_simple"))
     {