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MDEV-21248: Prevent optimizing out buf argument in check_stack_overrun.

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When using LTO, one can see optimization of stack variables that
are passed to check_stack_overrun as argument buf. That prevents
proper stack overrun detection.
This commit is contained in:
Martin Liska 2019-12-08 10:52:27 +01:00 committed by Anel
parent 0d1ca19383
commit 35c2778519
1 changed files with 11 additions and 2 deletions
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13
sql/sql_parse.cc
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@ -7392,8 +7392,17 @@ long max_stack_used;
corresponding exec. (Thus we only have to check in fix_fields.) corresponding exec. (Thus we only have to check in fix_fields.)
- Passing to check_stack_overrun() prevents the compiler from removing it. - Passing to check_stack_overrun() prevents the compiler from removing it.
*/ */
bool check_stack_overrun(THD *thd, long margin,
uchar *buf __attribute__((unused))) bool
#ifdef __GNUC__
/*
Do not optimize the function in order to preserve a stack variable creation.
Otherwise, the variable pointed as "buf" can be removed due to a missing
usage.
*/
__attribute__((optimize("-O0")))
#endif
check_stack_overrun(THD *thd, long margin, uchar *buf __attribute__((unused)))
{ {
long stack_used; long stack_used;
DBUG_ASSERT(thd == current_thd); DBUG_ASSERT(thd == current_thd);