Confused by segfault with legitimate call to strerror(3) on amd64 / sysctl (3) setting `odd' errno's

[Christoph Mallon]

Garrett Cooper schrieb:
>     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;
> 
> }
> 
> [gcooper at optimus ~]$ gcc -o badfile badfile.c
> [gcooper at optimus ~]$ ./badfile
> Errno: 2
> Segmentation fault: 11 (core dumped)
> [gcooper at optimus ~]$

Well, compile with -g, start in gdb, check what value is wrong, the 
usual stuff. Probably the return value of strerror() is interesting.