https://bugs.kde.org/show_bug.cgi?id=489707
Bug ID: 489707
Summary: Conditional jump or move depends on uninitialised
value(s)" shouldn't apply to assertions.
Classification: Developer tools
Product: valgrind
Version: 3.23.0
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: memcheck
Assignee: jsew...@acm.org
Reporter: dan...@mariadb.org
Target Milestone: ---
SUMMARY
Defensive code can use assertions around uninitialised values to protect
against undefined behaviour. While valgrind does the same thing, to do both
there is now a different compile option to test under valgrind.
STEPS TO REPRODUCE
1. t.c
#include <assert.h>
int main()
{
unsigned long n;
char *b = (char *) &n;
*b = 1;
assert((n & ~0xFFUL) == 0);
}
2. gcc -o /tmp/t /tmp/t.c
3. valgrind /tmp/t
OBSERVED RESULT
==1111332== Conditional jump or move depends on uninitialised value(s)
==1111332== at 0x401147: main (in /tmp/t)
EXPECTED RESULT
no error.
SOFTWARE/OS VERSIONS
Linux (Fedora 40)
(gcc 14.1.1)
ADDITIONAL INFORMATION
This didn't trigger as error on valgrind 3.18.1.
ref: https://jira.mariadb.org/browse/MDEV-34502
and workaround: https://github.com/MariaDB/server/pull/3378
notably: valgrind didn't error on the subsequent statements reading n
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