Re: [RFC] linux: use __fd_to_filename helper function instead of snprintf.

[Florian Weimer <fweimer@redhat.com>]

* Érico Nogueira via Libc-alpha:

> diff --git a/sysdeps/unix/sysv/linux/fexecve.c b/sysdeps/unix/sysv/linux/fexecve.c
> index f37c245396..218337a3b5 100644
> --- a/sysdeps/unix/sysv/linux/fexecve.c
> +++ b/sysdeps/unix/sysv/linux/fexecve.c
> @@ -22,6 +22,7 @@
>  #include <fcntl.h>
>  #include <sys/stat.h>
>  
> +#include <fd_to_filename.h>
>  #include <sysdep.h>
>  #include <sys/syscall.h>
>  #include <kernel-features.h>
> @@ -50,8 +51,8 @@ fexecve (int fd, char *const argv[], char *const envp[])
>  #ifndef __ASSUME_EXECVEAT
>    /* We use the /proc filesystem to get the information.  If it is not
>       mounted we fail.  */
> -  char buf[sizeof "/proc/self/fd/" + sizeof (int) * 3];
> -  __snprintf (buf, sizeof (buf), "/proc/self/fd/%d", fd);
> +  struct fd_to_filename filename;
> +  char *buf = fd_to_filename(fd, &filename);

Sorry, this patch fails to build if applied to current master:

../sysdeps/unix/sysv/linux/fexecve.c: In function ‘fexecve’:
../sysdeps/unix/sysv/linux/fexecve.c:55:15: error: implicit declaration of function ‘fd_to_filename’ [-Werror=implicit-function-declaration]
   55 |   char *buf = fd_to_filename(fd, &filename);
      |               ^~~~~~~~~~~~~~

Please also add a space before the opening '(', to match GNU style, and
consider if the code becomes clearer if you avoid the buf variable.

Thanks,
Florian