On Fri, Jan 16, 2009 at 2:21 AM, Christoph Mallon
<[email protected]> wrote:
> Christian Kandeler schrieb:
>>
>> On Friday 16 January 2009 09:53, Christoph Mallon wrote:
>>
>>>> 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.
>>
>> I don't think printf() can set errno. And even if it could, it
>
> Of course it can. See ISO/IEC 9899:1999 (E) ยง7.5:3.
>
>> wouldn't matter, because C has call-by-value semantics.
>
> This has nothing to do with call-by-value. errno is read (even twice!)
> *after* the call to printf().
Ok, I just installworld'ed, recompiled the program with the
following modifications, and I still get segfaults. And the question
of the night is: why amd64 on a VERY recent CURRENT?
I'm going to try the same app on an amd64 freebsd VMware instance
with RELENG_7.
Remember: just because a bunch of other people aren't reporting
issues with CURRENT/amd64 doesn't mean that it isn't environmental,
related to my hardware or compile options ;).
Cheers,
-Garrett
#include <errno.h>
#include <stdio.h>
#include <sys/stat.h>
int
main()
{
struct stat sb;
int o_errno;
if (stat("/some/file/that/doesn't/exist", &sb) != 0) {
o_errno = errno;
printf("Errno: %d\n", errno);
printf("%s\n", strerror(o_errno));
}
return 0;
}
#include <errno.h>
#include <stdio.h>
#include <sys/stat.h>
int
main()
{
struct stat sb;
int o_errno;
if (stat("/some/file/that/doesn't/exist", &sb) != 0) {
o_errno = errno;
printf("Errno: %d\n", errno);
printf("%s\n", strerror(o_errno));
}
return 0;
}
[gcoo...@optimus ~]$ gcc -o badfile badfile.c
[gcoo...@optimus ~]$ ./badfile
Errno: 2
Segmentation fault: 11 (core dumped)
[gcoo...@optimus ~]$
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