https://bugs.kde.org/show_bug.cgi?id=455711
Bug ID: 455711
Summary: Syscall param sigaltstack(ss) points to uninitialised
byte(s) when only ss.ss_flags = SS_DISABLE
Product: valgrind
Version: unspecified
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: memcheck
Assignee: jsew...@acm.org
Reporter: rjo...@redhat.com
Target Milestone: ---
SUMMARY
The OCaml compiler calls sigaltstack using code similar to this:
#include <stdlib.h>
#include <signal.h>
int
main ()
{
stack_t ss;
ss.ss_flags = SS_DISABLE;
sigaltstack (&ss, NULL);
}
According to the docs this is fine, you don't need to initialize the other
fields in the struct if you are disabling the alternate stack. However
valgrind complains:
==382696== Syscall param sigaltstack(ss) points to uninitialised byte(s)
==382696== at 0x48AD42B: sigaltstack (syscall-template.S:120)
==382696== by 0x401145: main (in /var/tmp/sigaltstack)
==382696== Address 0x1ffefff930 is on thread 1's stack
==382696== in frame #1, created by main (???:)
This happens when running any OCaml program under valgrind. Original bug
report:
https://github.com/ocaml/ocaml/issues/11335
https://github.com/ocaml/ocaml/blob/2c2e99049a5189bb874d215968435cc1e8a375ea/runtime/signals_nat.c#L349
STEPS TO REPRODUCE
1. Compile the above program and run it under valgrind.
SOFTWARE/OS VERSIONS
Linux: Fedora 37 valgrind-3.19.0-3.fc37.x86_64
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