[LTP] [RFC][PATCH 1/2] sched/process.c: Always use pointer to stderr

[Li Wang]

On Sat, Sep 4, 2021 at 5:48 AM Petr Vorel <petr.vorel@gmail.com> wrote:

> which was previously used for non-linux OS (not relevant to LTP thus not
> used in LTP), for linux stderr directly was used.
>
> This fixes compilation on MUSL which does not like assignment to stderr:
>
> process.c:553:14: error: assignment of read-only variable 'stderr'
>   553 |      debugfp = fopen(foo, "a+");
>       |              ^
>
> NOTE: needed to initialization in main(), because C standard does not
> require stdin, stdout and stderr to be constants (at least not C99),
> otherwise it fails to compile:
>
> process.c:144:15: error: initializer element is not constant
>
> Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
> ---
> Hi,
>
> not really sure why anything needs to be assigned to stderr and whether
> this is a correct approach. Comments are welcome.
>

Hmm, I guess that the original purpose is to redirect stderr to
another destination. But it made a mistake which assigns new
FILE stream to stderr, AFAIK, we should not do like that.
A recomened way is:
    FILE *debugfp = freopen(foo, "w", stderr );

Or, it just wants to make compatible but forget that definition in use then.


Anyway, your fix looks good.
Reviewed-by: Li Wang <liwang@redhat.com>



>
> Kind regards,
> Petr
>
>  testcases/kernel/sched/process_stress/process.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/testcases/kernel/sched/process_stress/process.c
> b/testcases/kernel/sched/process_stress/process.c
> index a5ff80987..11837c3cb 100644
> --- a/testcases/kernel/sched/process_stress/process.c
> +++ b/testcases/kernel/sched/process_stress/process.c
> @@ -141,13 +141,8 @@ timer_t timer;                     /* timer structure
> */
>
>  Pinfo *shmaddr;                        /* Start address  of shared memory
> */
>
> -#ifndef _LINUX
> -FILE *errfp = stderr;          /* error file pointer, probably not
> necessary */
> -FILE *debugfp = stderr;                /* debug file pointer, used if
> AUSDEBUG set */
> -#else
> -#define errfp stderr
> -#define debugfp stderr
> -#endif
> +FILE *errfp;
> +FILE *debugfp;
>
>  struct envstruct *edat = envdata;      /* pointer to environment data */
>
> @@ -1221,6 +1216,9 @@ void doit(void)
>  /* main */
>  int main(int argc, char *argv[])
>  {
> +       errfp = stderr;
> +       debugfp = stderr;
> +
>         extern Pinfo *shmaddr;  /* start address of shared memory */
>
>         prtln();
> --
> 2.33.0
>
>
> --
> Mailing list info: https://lists.linux.it/listinfo/ltp
>
>

-- 
Regards,
Li Wang
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