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.
---
gcc/c-family/c-pch.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
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
--
Dodji
