setrlimit always fails

[Corinna Vinschen]

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