| Message ID | m3y5ylhfbz.fsf@redhat.com |
|---|---|
| State | New |
| Headers | show |
On 11-08-22 07:10 , Dodji Seketeli wrote: > Hello, > > In c_common_read_pch when gt_pch_restore loads a new pch, the previous > line table (referenced from the global 'line_table') is > garbage-collected and a new one is built. > > As the global instance of cpp_reader referenced by the local variable > 'pfile' has a pfile->line_table member that references the > 'line_table' global, pfile->line_table needs to be set to the new > value of line_table after gt_pch_restore is called, otherwise > pfile->line_table points to garbage-collected memory. This is what > the call to cpp_set_line_map in c_common_read_pch is for. > > The problem is that cpp_set_line_map is called too late as > cpp_read_state (called before cpp_set_line_map) indirectly touches > some pfile->line_table dangling garbage-collected memory[1]. > > This doesn't cause any visible havoc in trunk yet but I am seeing it > crashing as I am fiddling with line map stuff on the side. > > The two-liner patch below just calls cpp_set_line_map right after > gt_pch_restore to restore pfile->line_table before anyone touches it. > > [1]: This happens via cpp_read_state -> _cpp_create_definition -> > _cpp_create_iso_definition -> _cpp_lex_token -> _cpp_lex_direct -> > linemap_position_for_column. > > Bootstrapped and tested on x86_64-unknown-linux-gnu against trunk. > > OK for trunk? > > gcc/ > > * c-family/c-pch.c (c_common_read_pch): Re-set line table right > after reading in the pch. OK. Diego.
Diego Novillo <dnovillo@google.com> writes: > On 11-08-22 07:10 , Dodji Seketeli wrote: [...] >> gcc/ >> >> * c-family/c-pch.c (c_common_read_pch): Re-set line table right >> after reading in the pch. > > OK. Thanks, committed to revision r177964.
diff --git a/gcc/c-family/c-pch.c b/gcc/c-family/c-pch.c index b429d9d..3c2fd18 100644 --- a/gcc/c-family/c-pch.c +++ b/gcc/c-family/c-pch.c @@ -431,6 +431,7 @@ c_common_read_pch (cpp_reader *pfile, const char *name, timevar_pop (TV_PCH_CPP_RESTORE); gt_pch_restore (f); + cpp_set_line_map (pfile, line_table); timevar_push (TV_PCH_CPP_RESTORE); if (cpp_read_state (pfile, name, f, smd) != 0) @@ -445,7 +446,6 @@ c_common_read_pch (cpp_reader *pfile, const char *name, fclose (f); line_table->trace_includes = saved_trace_includes; - cpp_set_line_map (pfile, line_table); linemap_add (line_table, LC_RENAME, 0, saved_loc.file, saved_loc.line); /* Give the front end a chance to take action after a PCH file has