Re: [libvirt] [PATCH] virsh: change wexitstatus order to allow compilation on mac osx
[adding bug-gnulib; replies can drop libvir-list]
>> - if (command_ret != WEXITSTATUS (0)) {
>> + if (WEXITSTATUS(command_ret) != 0) {
>
> ACK. By the way, what was the compilation failure?
Thanks, pushed. The compilation failure was:
virsh.c:8605: error: lvalue required as unary '&' operand
Which seems weird, but this patch really did fix it. :)
Aha - the darwin <sys/wait.h> contains:
#if defined(_POSIX_C_SOURCE) && !defined(_DARWIN_C_SOURCE)
#define _W_INT(i) (i)
#else
#define _W_INT(w) (*(int *)&(w)) /* convert union wait to int */
#define WCOREFLAG 0200
#endif /* (_POSIX_C_SOURCE && !_DARWIN_C_SOURCE) */
...
#if __DARWIN_UNIX03
#define WEXITSTATUS(x) ((_W_INT(x) >> 8) & 0x000000ff)
#else /* !__DARWIN_UNIX03 */
#define WEXITSTATUS(x) (_W_INT(x) >> 8)
#endif /* !__DARWIN_UNIX03 */
...
union wait {
int w_status; /* used in syscall */
/*
* Terminated process status.
*/
struct {
#if __DARWIN_BYTE_ORDER == __DARWIN_LITTLE_ENDIAN
unsigned int w_Termsig:7, /* termination signal */
w_Coredump:1, /* core dump indicator */
w_Retcode:8, /* exit code if
w_termsig==0 */
w_Filler:16; /* upper bits filler */
#endif
#if __DARWIN_BYTE_ORDER == __DARWIN_BIG_ENDIAN
unsigned int w_Filler:16, /* upper bits filler */
w_Retcode:8, /* exit code if
w_termsig==0 */
w_Coredump:1, /* core dump indicator */
w_Termsig:7; /* termination signal */
#endif
} w_T;
/*
* Stopped process status. Returned
* only for traced children unless requested
* with the WUNTRACED option bit.
*/
struct {
#if __DARWIN_BYTE_ORDER == __DARWIN_LITTLE_ENDIAN
unsigned int w_Stopval:8, /* == W_STOPPED if
stopped */
w_Stopsig:8, /* signal that stopped
us */
w_Filler:16; /* upper bits filler */
#endif
#if __DARWIN_BYTE_ORDER == __DARWIN_BIG_ENDIAN
unsigned int w_Filler:16, /* upper bits filler */
w_Stopsig:8, /* signal that stopped
us */
w_Stopval:8; /* == W_STOPPED if
stopped */
#endif
} w_S;
};
Obviously, the Darwin folks are (mistakenly) assuming that you would
only ever use WEXITSTATUS with a 'union wait' lvalue; in which case,
(*(int*)&(0)) is indeed invalid C (notice that they do the right thing
if you request POSIX compliance with _POSIX_C_SOURCE, but since gnulib
[rightfully] wants to expose and take advantage of system extensions, we
can't define _POSIX_C_SOURCE). Since WEXITSTATUS should be usable on
constants; it is a bug in their headers, and one that Gnulib should be
able to work around.
--
Eric Blake eblake(a)redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org