Control: found -1 1:3.19.0-1

On 2020-06-13 20:06:26 +0200, Vincent Lefevre wrote:

Package: valgrind
Version: 1:3.15.0-1
Severity: normal

When testing GNU MPFR with valgrind:

[...]

Note that this is no longer reproducible with the latest version of
the MPFR (or perhaps I need to pass some specific configure options,
I don't remember...). Anyway, the issue is still reproducible with a
simple testcase:

#include <stdlib.h>
int main (void)
{
void *p = malloc ((size_t) -1);
return p != NULL;
}

qaa% gcc-snapshot tst.c -o tst
tst.c: In function 'main':
tst.c:4:13: warning: argument 1 value '18446744073709551615' exceeds maximum object size 9223372036854775807 [-Walloc-size-larger-than=]
4 | void *p = malloc ((size_t) -1);
| ^~~~~~~~~~~~~~~~~~~~
In file included from tst.c:1:
/usr/include/stdlib.h:672:14: note: in a call to allocation function 'malloc' declared here
672 | extern void *malloc (size_t __size) __THROW __attribute_malloc__
| ^~~~~~
qaa% valgrind ./tst
[...]
==1153312== Argument 'size' of function malloc has a fishy (possibly negative) value: -1
==1153312== at 0x48437B4: malloc (vg_replace_malloc.c:381)
==1153312== by 0x401139: main (in /home/vinc17/tst)
[...]

GCC is right about the value (a very large positive value) in its
warning, but valgrind is still wrong as seeing it as negative.

--
Vincent LefΦvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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