https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81405
--- Comment #3 from David Malcolm <dmalcolm at gcc dot gnu.org> --- Author: dmalcolm Date: Thu Jul 13 19:30:42 2017 New Revision: 250187 URL: https://gcc.gnu.org/viewcvs?rev=250187&root=gcc&view=rev Log: diagnostics: fix crash when consolidating out-of-order fix-it hints (PR c/81405) PR c/81405 identifies a crash when printing fix-it hints from -Wmissing-braces when there are excess elements. The fix-it hints are bogus (which I've filed separately as PR c/81432), but they lead to a crash within the fix-it consolidation logic I added in r247548, in line_corrections::add_hint. The root cause is that some of the fix-it hints are out-of-order with respect to the column numbers they affect, which can lead to negative values when computing the gap between the fix-it hints, leading to bogus memcpy calls that generate out-of-bounds buffer accesses. The fix is to sort the fix-it hints after filtering them, ensuring that the gap >= 0. The patch also adds numerous assertions to the code, both directly, and by moving the memcpy calls and their args behind interfaces (themselves containing gcc_assert). This fixes the crash; it doesn't fix the bug in -Wmissing-braces that leads to the bogus hints. gcc/ChangeLog: PR c/81405 * diagnostic-show-locus.c (fixit_cmp): New function. (layout::layout): Sort m_fixit_hints. (column_range::column_range): Assert that the values are valid. (struct char_span): New struct. (correction::overwrite): New method. (struct source_line): New struct. (line_corrections::add_hint): Add assertions. Reimplement memcpy calls in terms of classes source_line and char_span, and correction::overwrite. (selftest::test_overlapped_fixit_printing_2): New function. (selftest::diagnostic_show_locus_c_tests): Call it. gcc/testsuite/ChangeLog: PR c/81405 * gcc.dg/Wmissing-braces-fixits.c: Add coverage for PR c/81405. */ Modified: trunk/gcc/ChangeLog trunk/gcc/diagnostic-show-locus.c trunk/gcc/testsuite/ChangeLog trunk/gcc/testsuite/gcc.dg/Wmissing-braces-fixits.c
