From 6e46b3f3da5c03bc529b3690dd0995927feb9142 Mon Sep 17 00:00:00 2001 From: Sergei Trofimovich Date: Sun, 2 Aug 2020 12:03:55 +0100 Subject: [PATCH] var-tracking: fix uninitialised use of 'in_pending' [PR96404] r11-2447-g:1212cfad093 ("Improve var-tracking dataflow iteration order") changed 'in_pending' initialization from: in_pending = sbitmap_alloc (last_basic_block_for_fn (cfun)); bitmap_ones (in_pending); to more complex partial bit population algorithm. Due to presence of uninitialized bits gcc started injecting extra debug entries in seemigly arbitrary locations and started failing stage2/stage3 bootstrap comparison. valgrind detected unilitialized bits as: Conditional jump or move depends on uninitialised value(s) at 0xDBED3B: vt_find_locations() (var-tracking.c:7230) by 0xDBF2FB: variable_tracking_main_1() (var-tracking.c:10519) ... Uninitialised value was created by a heap allocation at 0x483779F: malloc (vg_replace_malloc.c:307) by 0x14EE80B: xmalloc (xmalloc.c:147) by 0x14911F9: sbitmap_alloc(unsigned int) (sbitmap.c:51) ... The fix explicitly initializes 'in_pending' bitmap with zeros. 2020-08-02 Sergei Trofimovich gcc/ PR bootstrap/96404 * var-tracking.c (vt_find_locations): Fully initialize all 'in_pending' bits. --- gcc/var-tracking.c | 1 + 1 file changed, 1 insertion(+) diff --git a/gcc/var-tracking.c b/gcc/var-tracking.c index 743f5dcecf6..52aea47a053 100644 --- a/gcc/var-tracking.c +++ b/gcc/var-tracking.c @@ -7096,6 +7096,7 @@ vt_find_locations (void) in_worklist = sbitmap_alloc (last_basic_block_for_fn (cfun)); in_pending = sbitmap_alloc (last_basic_block_for_fn (cfun)); bitmap_clear (in_worklist); + bitmap_clear (in_pending); /* We're performing the dataflow iteration independently over the toplevel SCCs plus leading non-cyclic entry blocks and separately -- 2.30.2