Garrett Cooper schrieb:
Hi amd64 and Hackers,
Uh, I'm really confused why 1) this error (errno => ENOMEM) would
occur when I have more than enough free memory (both on x86 and amd64)
and 2) why strerror would segfault in the call to errx in the attached
sourcefile on amd64 only. Not initializing len causes the second
output sample (errno => 14, which is EFAULT).
Any ideas?
Please CC me if mailing on amd64@ as I'm not subscribed to the list.
Thanks,
-Garrett
len is not uninitialised. This leads to undefined behaviour. Anything
can happen. Probably the syscall overwrites parts of the stack because
len has some (random) high value.
/* Program */
#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/sysctl.h>
int
main() {
int mib[4];
size_t len;
if (sysctlnametomib("kern.ipc.shmmax", mib, &len) != 0) {
printf("Errno: %d\n", errno);
errx(errno, "Error: %s", strerror(errno));
The use of errno is wrong. printf might change errno. Store the errno
into a local variable before you do any call, which might modify it.
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