https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106503
Bug ID: 106503
Summary: "const char []" in local scope never initialized
Product: gcc
Version: 11.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: eb at emlix dot com
Target Milestone: ---
Given the following test program:
------------
#include <sys/uio.h>
#include <string.h>
#define WRITEL(str) \
do { \
wdata[wpos].iov_base = (void*)(str); \
wdata[wpos].iov_len = strlen(str); \
wlen += wdata[wpos].iov_len; \
wpos++; \
} while (0)
int main(int argc, char **argv)
{
struct iovec wdata[20];
unsigned int wpos = 0;
ssize_t wlen = 0;
int i = (argc > 1) ? 1 : 0;
WRITEL("foo");
if (argc) {
const char junk[] = "abc";
WRITEL(junk + i);
} else {
const char *junk = "def";
WRITEL(junk + i);
}
WRITEL("baz\n");
return writev(1, wdata, wpos) > 0 ? 0 : 1;
}
------------
For gcc 10 and before, and gcc 11, 12, or 13
(b06a282921c71bbc5cab69bc515804bd80f55e92) when used with -O0, this outputs:
$ ./Ch
fooabcbaz
>From gcc 11 on when using -O1 or more it does not seem to initialize the "junk"
buffer, so it may output random things:
$ ./Ch
foocbaz
$ ./Ch
foo�baz
$ ./Ch
foo+baz
$ ./Ch
foo baz
$ ./Ch
foo[baz
I have seen the same behavior on both amd64 and sparc32, with distro compilers
(openSUSE, Gentoo) as well as an unpatched gcc13 built with Gentoo ebuilds.
