https://bugs.kde.org/show_bug.cgi?id=474339
Bug ID: 474339
Summary: aligned_alloc with alignment less than
VG_MIN_MALLOC_SZB causes Valgrind to panic
Classification: Developer tools
Product: valgrind
Version: unspecified
Platform: Archlinux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: memcheck
Assignee: jsew...@acm.org
Reporter: smj...@gmail.com
Target Milestone: ---
SUMMARY
This is somewhat connected to https://bugs.kde.org/show_bug.cgi?id=474332,
because if I do a workaround for this here:
https://sourceware.org/git/?p=valgrind.git;a=blob;f=coregrind/m_mallocfree.c;h=44beb3d8b57cc3d7859a2966b4f5824e255fb6d4;hb=23250889de4e2079ad1ede6874cc824bc9dd92db#l2258,
by removing the panic and setting req_alignB to VG_MIN_MALLOC_SZB, I hit the
other issue.
I'm using Valgrind on master, at commit:
d4c9a98527afdbd67b25a1300339a42b9e0a24c2
STEPS TO REPRODUCE
1. Compile and run the following C snippet:
#include <stdlib.h>
#include <stdio.h>
int main() {
char *p = aligned_alloc(4, 4);
if(p == NULL) {
printf("Allocation failed!\n");
return 1;
}
printf("Allocation succeeded!\n");
return 0;
}
2. Then run it again under Valgrind
OBSERVED RESULT
The allocation succeeds when run on its own, but with Valgrind fails:
VG_(arena_memalign)(0x58889810, 4, 4)
bad alignment value 4
(it is too small, below the lower limit of 16)
valgrind: the 'impossible' happened:
VG_(arena_memalign)
EXPECTED RESULT
Both succeeds.
ADDITIONAL INFORMATION
The issue seems to be similar to the other bug I linked above, but here the
requirement on the alignment seems to be more strict and actually connected to
what's required from malloc, but not aligned_alloc, which again is
implementation dependent and on glibc the only limit seems to be that it has to
be a power of 2.
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