On Feb 15 14:54, Patrick Chkoreff wrote:
> Corinna Vinschen wrote on 2/15/21 4:14 AM:
>
> > That looks wrong. The __USE_<standard> flags are internal flags from
> > GLibc and not supposed to be used by application code. Check the Linux
> > man page for strptime, the usage of _XOPEN_SOURCE or another flag
> > including _XOPEN_SOURCE (e. g. _GNU_SOURCE) is required. So this:
> >
> > #define _XOPEN_SOURCE
> > #include <time.h>
>
> One would think so, but I tried it on two different Linux machines and
> it failed with:
>
> error: ‘strptime’ undeclared
>
> To fix that, I must define _USE_XOPEN
You really, really must not use this macro.
> #else
>
> #include <stdint.h>
> #include <sys/time.h>
> #define __USE_XOPEN
> #include <time.h>
>
> #endif
>
> void stuff(void)
> {
> uint64_t n;
> time_t t;
> struct timeval tv;
> (void)n;
> (void)t;
> (void)tv;
> (void)time;
> (void)gettimeofday;
> (void)timegm;
> (void)timelocal;
> (void)gmtime;
> (void)localtime;
> (void)strftime;
> (void)strptime;
> }
The problem here is that you mix functions only defined under
_XOPEN_SOURCE with stuff only defined with _DEFAULT_SOURCE from the same
header. Either define both feature test macros, or define _GNU_SOURCE.
This works:
#define _XOPEN_SOURCE
#define _DEFAULT_SOURCE
#include <stdint.h>
#include <sys/time.h>
#include <time.h>
void stuff(void)
[...]
This works, too:
#define _GNU_SOURCE
#include <stdint.h>
#include <sys/time.h>
#include <time.h>
void stuff(void)
[...]
Corinna
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