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authorDavid Malcolm <dmalcolm@redhat.com>2017-01-07 21:33:59 +0000
committerDavid Malcolm <dmalcolm@gcc.gnu.org>2017-01-07 21:33:59 +0000
commit5ccf1d8d1073544f3d3c24e2168fc12e983dfa47 (patch)
treed50cf2a1d95d451c655a244f774cbcdbb459d9df /gcc
parentff98fa955b5dc98bb05e30ed79299155d2a2f97c (diff)
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Fix linemap corruption after very wide source lines (PR c++/72803)
PR c++/72803 describes an issue where a fix-it hint is to be emitted at column 512 of a 511-column source line, leading to an ICE. The root cause is a bug in linemap_line_start, when transitioning from lines >= 512 in width to narrow lines. The wide line in the reproducer has a line map with: m_column_and_range_bits = 15, m_range_bits = 5 giving 10 effective bits for representing columns, so that columns <= 1023 can be represented. When parsing the following line, linemap_line_start (..., ..., max_column_hint=0); is called. This leads to the "add_map" logic, due to this condition: || (max_column_hint <= 80 && effective_column_bits >= 10) i.e. the new line is sufficiently narrower than the old one to potentially use a new linemap (so as to conserve values within the location_t space). It then attempts to avoid allocating a new line map. Part of the logic to determine if we really need a new line map is this condition: SOURCE_COLUMN (map, highest) >= (1U << column_bits) The above condition is incorrect: we need to determine if the highest column we've handed out will fit within the proposed *effective* column bits, but "column_bits" here is the column plus the range bits, rather than just the column bits. Hence in this case linemap_line_start erroneously decides that we don't need a new line map, and updates the column bits within the existing line map, so any location_t values we've already handed out within it that are offset from the start by >= (1<<new_column_and_range_bits) effectively change meaning, leading to incorrect line&column information when decoding them, and various "interesting" ways for the linemap code to fail. The fix is to use the effective column bits in the above conditional. gcc/ChangeLog: PR c++/72803 * input.c (selftest::test_accessing_ordinary_linemaps): Verify that the transition from a max line width >= 1<<10 to narrower lines works correctly. gcc/testsuite/ChangeLog: PR c++/72803 * g++.dg/diagnostic/pr72803.C: New test case. libcpp/ChangeLog: PR c++/72803 * line-map.c (linemap_line_start): When determining if the highest column given out so far will fit into a proposed change to the current map, use the effective number of column bits, rather than the total number of column + range bits. From-SVN: r244199
Diffstat (limited to 'gcc')
-rw-r--r--gcc/ChangeLog7
-rw-r--r--gcc/input.c12
-rw-r--r--gcc/testsuite/ChangeLog5
-rw-r--r--gcc/testsuite/g++.dg/diagnostic/pr72803.C9
4 files changed, 33 insertions, 0 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 9f7f090..38b6102 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2017-01-07 David Malcolm <dmalcolm@redhat.com>
+
+ PR c++/72803
+ * input.c (selftest::test_accessing_ordinary_linemaps): Verify
+ that the transition from a max line width >= 1<<10 to narrower
+ lines works correctly.
+
2017-01-07 Alexandre Oliva <aoliva@redhat.com>
* doc/options.texi (PerFunction): New.
diff --git a/gcc/input.c b/gcc/input.c
index 195f72e..bbb6abb 100644
--- a/gcc/input.c
+++ b/gcc/input.c
@@ -1688,6 +1688,17 @@ test_accessing_ordinary_linemaps (const line_table_case &case_)
linemap_line_start (line_table, 3, 2000);
location_t loc_e = linemap_position_for_column (line_table, 700);
+ /* Transitioning back to a short line. */
+ linemap_line_start (line_table, 4, 0);
+ location_t loc_back_to_short = linemap_position_for_column (line_table, 100);
+
+ if (should_have_column_data_p (loc_back_to_short))
+ {
+ /* Verify that we switched to short lines in the linemap. */
+ line_map_ordinary *map = LINEMAPS_LAST_ORDINARY_MAP (line_table);
+ ASSERT_EQ (7, map->m_column_and_range_bits - map->m_range_bits);
+ }
+
linemap_add (line_table, LC_LEAVE, false, NULL, 0);
/* Multiple files. */
@@ -1702,6 +1713,7 @@ test_accessing_ordinary_linemaps (const line_table_case &case_)
assert_loceq ("foo.c", 2, 1, loc_c);
assert_loceq ("foo.c", 2, 17, loc_d);
assert_loceq ("foo.c", 3, 700, loc_e);
+ assert_loceq ("foo.c", 4, 100, loc_back_to_short);
assert_loceq ("bar.c", 1, 150, loc_f);
ASSERT_FALSE (is_location_from_builtin_token (loc_a));
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 340ec41..1f6100b 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-01-07 David Malcolm <dmalcolm@redhat.com>
+
+ PR c++/72803
+ * g++.dg/diagnostic/pr72803.C: New test case.
+
2017-01-07 Martin Sebor <msebor@redhat.com>
* gcc.dg/attr-alloc_size-3.c: Remove regex made redundant by r243461.
diff --git a/gcc/testsuite/g++.dg/diagnostic/pr72803.C b/gcc/testsuite/g++.dg/diagnostic/pr72803.C
new file mode 100644
index 0000000..0a9a390
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/pr72803.C
@@ -0,0 +1,9 @@
+/* Long line, with a close brace at column 511, hence with the insertion
+ point for the missing semicolon at column 512. */
+class test { }
+# 1 "" 1
+// The line directive appears to be necessary to trigger the ICE
+// { dg-error "style of line directive is a GCC extension" "" { target *-*-* } .-2 }
+
+/* Verify that we get the correct line and column for the diagnostic. */
+// { dg-error "512: expected .;. after class definition" "" { target *-*-* } 3 }