Historically, it was a global.
In modern times, "errno" is a macro that calls a private function (I
think it's called __error() or something). This allows it to be
thread-safe. By and large, though, you can treat it as if it were a
global variable.
George Malayil-Philip wrote:
Hi,
http://www.unix.org/whitepapers/reentrant.html
That should explain it. I think it is a globally defined variable which
is included by errno.h.
Regards
George M.P.
A few days ago, I asked if there was a way to detect if my program was
running under Rosetta. Several people sent me this link:
http://developer.apple.com/documentation/MacOSX/Conceptual/universal_binary/universal_binary_exec_a/chapter_7_section_7.html
However, the code there doesn't make any sense. Check out the 2nd
function:
int is_pid_native (pid_t pid)
{
int ret = 0;
size_t sz = sizeof(ret);
if
(sysctlbyname_with_pid("sysctl.proc_native", pid,
&ret, &sz, NULL, 0) == -1) {
if (errno == ENOENT) {
// sysctl doesn't exist, which means that this version of
Mac OS
// pre-dates Rosetta, so the application must be native.
return 1;
}
fprintf(stderr, "is_pid_native:
sysctlbyname_with_pid failed:"
"%s\n", strerror(errno));
return -1;
}
return ret;
}
Where is this "errno" variable that's being compared in the 2nd if
statement? It simply doesn't exist. Same for the first function
listing... it uses "errno" but errno isn't defined anywhere. Am I
really dense, or is this listing wrong?
I'd fix it if I knew what I was doing... Should it be using the "sz"
variable in place of errno?
-Vern
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