diagnostics: escape non-ASCII source bytes for certain diagnostics

This patch adds support to GCC's diagnostic subsystem for escaping certain
bytes and Unicode characters when quoting source code.

Specifically, this patch adds a new flag rich_location::m_escape_on_output
which is a hint from a diagnostic that non-ASCII bytes in the pertinent
lines of the user's source code should be escaped when printed.

The patch sets this for the following diagnostics:
- when complaining about stray bytes in the program (when these
are non-printable)
- when complaining about "null character(s) ignored");
- for -Wnormalized= (and generate source ranges for such warnings)

The escaping is controlled by a new option:
  -fdiagnostics-escape-format=[unicode|bytes]

For example, consider a diagnostic involing a source line containing the
string "before" followed by the Unicode character U+03C0 ("GREEK SMALL
LETTER PI", with UTF-8 encoding 0xCF 0x80) followed by the byte 0xBF
(a stray UTF-8 trailing byte), followed by the string "after", where the
diagnostic highlights the U+03C0 character.

By default, this line will be printed verbatim to the user when
reporting a diagnostic at it, as:

 beforeπXafter
       ^

(using X for the stray byte to avoid putting invalid UTF-8 in this
commit message)

If the diagnostic sets the "escape" flag, it will be printed as:

 before<U+03C0><BF>after
       ^~~~~~~~

with -fdiagnostics-escape-format=unicode (the default), or as:

  before<CF><80><BF>after
        ^~~~~~~~

if the user supplies -fdiagnostics-escape-format=bytes.

This only affects how the source is printed; it does not affect
how column numbers that are printed (as per -fdiagnostics-column-unit=
and -fdiagnostics-column-origin=).

gcc/c-family/ChangeLog:
	* c-lex.c (c_lex_with_flags): When complaining about non-printable
	CPP_OTHER tokens, set the "escape on output" flag.

gcc/ChangeLog:
	* common.opt (fdiagnostics-escape-format=): New.
	(diagnostics_escape_format): New enum.
	(DIAGNOSTICS_ESCAPE_FORMAT_UNICODE): New enum value.
	(DIAGNOSTICS_ESCAPE_FORMAT_BYTES): Likewise.
	* diagnostic-format-json.cc (json_end_diagnostic): Add
	"escape-source" attribute.
	* diagnostic-show-locus.c
	(exploc_with_display_col::exploc_with_display_col): Replace
	"tabstop" param with a cpp_char_column_policy and add an "aspect"
	param.  Use these to compute m_display_col accordingly.
	(struct char_display_policy): New struct.
	(layout::m_policy): New field.
	(layout::m_escape_on_output): New field.
	(def_policy): New function.
	(make_range): Update for changes to exploc_with_display_col ctor.
	(default_print_decoded_ch): New.
	(width_per_escaped_byte): New.
	(escape_as_bytes_width): New.
	(escape_as_bytes_print): New.
	(escape_as_unicode_width): New.
	(escape_as_unicode_print): New.
	(make_policy): New.
	(layout::layout): Initialize new fields.  Update m_exploc ctor
	call for above change to ctor.
	(layout::maybe_add_location_range): Update for changes to
	exploc_with_display_col ctor.
	(layout::calculate_x_offset_display): Update for change to
	cpp_display_width.
	(layout::print_source_line): Pass policy
	to cpp_display_width_computation. Capture cpp_decoded_char when
	calling process_next_codepoint.  Move printing of source code to
	m_policy.m_print_cb.
	(line_label::line_label): Pass in policy rather than context.
	(layout::print_any_labels): Update for change to line_label ctor.
	(get_affected_range): Pass in policy rather than context, updating
	calls to location_compute_display_column accordingly.
	(get_printed_columns): Likewise, also for cpp_display_width.
	(correction::correction): Pass in policy rather than tabstop.
	(correction::compute_display_cols): Pass m_policy rather than
	m_tabstop to cpp_display_width.
	(correction::m_tabstop): Replace with...
	(correction::m_policy): ...this.
	(line_corrections::line_corrections): Pass in policy rather than
	context.
	(line_corrections::m_context): Replace with...
	(line_corrections::m_policy): ...this.
	(line_corrections::add_hint): Update to use m_policy rather than
	m_context.
	(line_corrections::add_hint): Likewise.
	(layout::print_trailing_fixits): Likewise.
	(selftest::test_display_widths): New.
	(selftest::test_layout_x_offset_display_utf8): Update to use
	policy rather than tabstop.
	(selftest::test_one_liner_labels_utf8): Add test of escaping
	source lines.
	(selftest::test_diagnostic_show_locus_one_liner_utf8): Update to
	use policy rather than tabstop.
	(selftest::test_overlapped_fixit_printing): Likewise.
	(selftest::test_overlapped_fixit_printing_utf8): Likewise.
	(selftest::test_overlapped_fixit_printing_2): Likewise.
	(selftest::test_tab_expansion): Likewise.
	(selftest::test_escaping_bytes_1): New.
	(selftest::test_escaping_bytes_2): New.
	(selftest::diagnostic_show_locus_c_tests): Call the new tests.
	* diagnostic.c (diagnostic_initialize): Initialize
	context->escape_format.
	(convert_column_unit): Update to use default character width policy.
	(selftest::test_diagnostic_get_location_text): Likewise.
	* diagnostic.h (enum diagnostics_escape_format): New enum.
	(diagnostic_context::escape_format): New field.
	* doc/invoke.texi (-fdiagnostics-escape-format=): New option.
	(-fdiagnostics-format=): Add "escape-source" attribute to examples
	of JSON output, and document it.
	* input.c (location_compute_display_column): Pass in "policy"
	rather than "tabstop", passing to
	cpp_byte_column_to_display_column.
	(selftest::test_cpp_utf8): Update to use cpp_char_column_policy.
	* input.h (class cpp_char_column_policy): New forward decl.
	(location_compute_display_column): Pass in "policy" rather than
	"tabstop".
	* opts.c (common_handle_option): Handle
	OPT_fdiagnostics_escape_format_.
	* selftest.c (temp_source_file::temp_source_file): New ctor
	overload taking a size_t.
	* selftest.h (temp_source_file::temp_source_file): Likewise.

gcc/testsuite/ChangeLog:
	* c-c++-common/diagnostic-format-json-1.c: Add regexp to consume
	"escape-source" attribute.
	* c-c++-common/diagnostic-format-json-2.c: Likewise.
	* c-c++-common/diagnostic-format-json-3.c: Likewise.
	* c-c++-common/diagnostic-format-json-4.c: Likewise, twice.
	* c-c++-common/diagnostic-format-json-5.c: Likewise.
	* gcc.dg/cpp/warn-normalized-4-bytes.c: New test.
	* gcc.dg/cpp/warn-normalized-4-unicode.c: New test.
	* gcc.dg/encoding-issues-bytes.c: New test.
	* gcc.dg/encoding-issues-unicode.c: New test.
	* gfortran.dg/diagnostic-format-json-1.F90: Add regexp to consume
	"escape-source" attribute.
	* gfortran.dg/diagnostic-format-json-2.F90: Likewise.
	* gfortran.dg/diagnostic-format-json-3.F90: Likewise.

libcpp/ChangeLog:
	* charset.c (convert_escape): Use encoding_rich_location when
	complaining about nonprintable unknown escape sequences.
	(cpp_display_width_computation::::cpp_display_width_computation):
	Pass in policy rather than tabstop.
	(cpp_display_width_computation::process_next_codepoint): Add "out"
	param and populate *out if non-NULL.
	(cpp_display_width_computation::advance_display_cols): Pass NULL
	to process_next_codepoint.
	(cpp_byte_column_to_display_column): Pass in policy rather than
	tabstop.  Pass NULL to process_next_codepoint.
	(cpp_display_column_to_byte_column): Pass in policy rather than
	tabstop.
	* errors.c (cpp_diagnostic_get_current_location): New function,
	splitting out the logic from...
	(cpp_diagnostic): ...here.
	(cpp_warning_at): New function.
	(cpp_pedwarning_at): New function.
	* include/cpplib.h (cpp_warning_at): New decl for rich_location.
	(cpp_pedwarning_at): Likewise.
	(struct cpp_decoded_char): New.
	(struct cpp_char_column_policy): New.
	(cpp_display_width_computation::cpp_display_width_computation):
	Replace "tabstop" param with "policy".
	(cpp_display_width_computation::process_next_codepoint): Add "out"
	param.
	(cpp_display_width_computation::m_tabstop): Replace with...
	(cpp_display_width_computation::m_policy): ...this.
	(cpp_byte_column_to_display_column): Replace "tabstop" param with
	"policy".
	(cpp_display_width): Likewise.
	(cpp_display_column_to_byte_column): Likewise.
	* include/line-map.h (rich_location::escape_on_output_p): New.
	(rich_location::set_escape_on_output): New.
	(rich_location::m_escape_on_output): New.
	* internal.h (cpp_diagnostic_get_current_location): New decl.
	(class encoding_rich_location): New.
	* lex.c (skip_whitespace): Use encoding_rich_location when
	complaining about null characters.
	(warn_about_normalization): Generate a source range when
	complaining about improperly normalized tokens, rather than just a
	point, and use encoding_rich_location so that the source code
	is escaped on printing.
	* line-map.c (rich_location::rich_location): Initialize
	m_escape_on_output.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>

1 files changed, 45 insertions, 18 deletions

diff --git a/libcpp/charset.c b/libcpp/charset.c
index e4e45f6..0b0ccc6 100644
--- a/libcpp/charset.c
+++ b/libcpp/charset.c
@@ -1582,12 +1582,14 @@ convert_escape (cpp_reader *pfile, const uchar *from, const uchar *limit,
 		   "unknown escape sequence: '\\%c'", (int) c);
       else
 	{
+	  encoding_rich_location rich_loc (pfile);
+
 	  /* diagnostic.c does not support "%03o".  When it does, this
 	     code can use %03o directly in the diagnostic again.  */
 	  char buf[32];
 	  sprintf(buf, "%03o", (int) c);
-	  cpp_error (pfile, CPP_DL_PEDWARN,
-		     "unknown escape sequence: '\\%s'", buf);
+	  cpp_error_at (pfile, CPP_DL_PEDWARN, &rich_loc,
+			"unknown escape sequence: '\\%s'", buf);
 	}
     }
 
@@ -2345,14 +2347,16 @@ cpp_string_location_reader::get_next ()
 }
 
 cpp_display_width_computation::
-cpp_display_width_computation (const char *data, int data_length, int tabstop) :
+cpp_display_width_computation (const char *data, int data_length,
+			       const cpp_char_column_policy &policy) :
   m_begin (data),
   m_next (m_begin),
   m_bytes_left (data_length),
-  m_tabstop (tabstop),
+  m_policy (policy),
   m_display_cols (0)
 {
-  gcc_assert (m_tabstop > 0);
+  gcc_assert (policy.m_tabstop > 0);
+  gcc_assert (policy.m_width_cb);
 }
 
 
@@ -2364,19 +2368,28 @@ cpp_display_width_computation (const char *data, int data_length, int tabstop) :
    point to a valid UTF-8-encoded sequence, then it will be treated as a single
    byte with display width 1.  m_cur_display_col is the current display column,
    relative to which tab stops should be expanded.  Returns the display width of
-   the codepoint just processed.  */
+   the codepoint just processed.
+   If OUT is non-NULL, it is populated.  */
 
 int
-cpp_display_width_computation::process_next_codepoint ()
+cpp_display_width_computation::process_next_codepoint (cpp_decoded_char *out)
 {
   cppchar_t c;
   int next_width;
 
+  if (out)
+    out->m_start_byte = m_next;
+
   if (*m_next == '\t')
     {
       ++m_next;
       --m_bytes_left;
-      next_width = m_tabstop - (m_display_cols % m_tabstop);
+      next_width = m_policy.m_tabstop - (m_display_cols % m_policy.m_tabstop);
+      if (out)
+	{
+	  out->m_ch = '\t';
+	  out->m_valid_ch = true;
+	}
     }
   else if (one_utf8_to_cppchar ((const uchar **) &m_next, &m_bytes_left, &c)
 	   != 0)
@@ -2386,14 +2399,24 @@ cpp_display_width_computation::process_next_codepoint ()
 	 of one.  */
       ++m_next;
       --m_bytes_left;
-      next_width = 1;
+      next_width = m_policy.m_undecoded_byte_width;
+      if (out)
+	out->m_valid_ch = false;
     }
   else
     {
       /*  one_utf8_to_cppchar() has updated m_next and m_bytes_left for us.  */
-      next_width = cpp_wcwidth (c);
+      next_width = m_policy.m_width_cb (c);
+      if (out)
+	{
+	  out->m_ch = c;
+	  out->m_valid_ch = true;
+	}
     }
 
+  if (out)
+    out->m_next_byte = m_next;
+
   m_display_cols += next_width;
   return next_width;
 }
@@ -2409,7 +2432,7 @@ cpp_display_width_computation::advance_display_cols (int n)
   const int start = m_display_cols;
   const int target = start + n;
   while (m_display_cols < target && !done ())
-    process_next_codepoint ();
+    process_next_codepoint (NULL);
   return m_display_cols - start;
 }
 
@@ -2417,29 +2440,33 @@ cpp_display_width_computation::advance_display_cols (int n)
     how many display columns are occupied by the first COLUMN bytes.  COLUMN
     may exceed DATA_LENGTH, in which case the phantom bytes at the end are
     treated as if they have display width 1.  Tabs are expanded to the next tab
-    stop, relative to the start of DATA.  */
+    stop, relative to the start of DATA, and non-printable-ASCII characters
+    will be escaped as per POLICY.  */
 
 int
 cpp_byte_column_to_display_column (const char *data, int data_length,
-				   int column, int tabstop)
+				   int column,
+				   const cpp_char_column_policy &policy)
 {
   const int offset = MAX (0, column - data_length);
-  cpp_display_width_computation dw (data, column - offset, tabstop);
+  cpp_display_width_computation dw (data, column - offset, policy);
   while (!dw.done ())
-    dw.process_next_codepoint ();
+    dw.process_next_codepoint (NULL);
   return dw.display_cols_processed () + offset;
 }
 
 /*  For the string of length DATA_LENGTH bytes that begins at DATA, compute
     the least number of bytes that will result in at least DISPLAY_COL display
     columns.  The return value may exceed DATA_LENGTH if the entire string does
-    not occupy enough display columns.  */
+    not occupy enough display columns.  Non-printable-ASCII characters
+    will be escaped as per POLICY.  */
 
 int
 cpp_display_column_to_byte_column (const char *data, int data_length,
-				   int display_col, int tabstop)
+				   int display_col,
+				   const cpp_char_column_policy &policy)
 {
-  cpp_display_width_computation dw (data, data_length, tabstop);
+  cpp_display_width_computation dw (data, data_length, policy);
   const int avail_display = dw.advance_display_cols (display_col);
   return dw.bytes_processed () + MAX (0, display_col - avail_display);
 }