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Re: [PATCH] powerpc: Fix compiler warning on some syscalls


On Tue, Jan 06, 2015 at 11:10:38AM -0200, Adhemerval Zanella wrote:
> GCC 5.0 emits an warning when using sizeof on array function parameters
> and powerpc internal syscall macros add an check for such cases.  More
> specifically, on powerpc64 and powerpc32 sysdep.h:
> 
>   if (__builtin_classify_type (__arg3) != 5 && sizeof (__arg3) > 8) \
>           __illegally_sized_syscall_arg3 (); \
> 
> And for sysdeps/unix/sysv/linux/utimensat.c build GCC emits:
> 
> error: âsizeofâ on array function parameter âtspâ will return size of
> âconst struct timespec *â
> 
> This patch adds explicit casts to struct pointers to avoid the warnings.
> 
> Checked on powerpc64 and powerpc32. Ok to push?
> 
> PS: it turned out my earlier checks were incorrect and I didn't see the
> issue when I updated my GCC because I used --disable-werror.
> 
> --
> 
> 	* sysdeps/unix/sysv/linux/futimens.c (futimens): Cast timespec struct
> 	argument to pointer.
> 	* sysdeps/unix/sysv/linux/utimensat.c (utimensat): Likewise.
> 	* sysdeps/unix/sysv/linux/futimesat.c (futimesat): Cast timeval struct
> 	argument to pointer.
> 	* sysdeps/unix/sysv/linux/utimes.c (__utimeS): Likewise.
> 
> --
> 
> diff --git a/sysdeps/unix/sysv/linux/futimens.c b/sysdeps/unix/sysv/linux/futimens.c
> index c7d03a8..c0e7219 100644
> --- a/sysdeps/unix/sysv/linux/futimens.c
> +++ b/sysdeps/unix/sysv/linux/futimens.c
> @@ -37,7 +37,11 @@ futimens (int fd, const struct timespec tsp[2])
>        __set_errno (EBADF);
>        return -1;
>      }
> -  return INLINE_SYSCALL (utimensat, 4, fd, NULL, tsp, 0);
> +  /* Some archs (powerpc) add arguments type and size check using sizeof
> +     and without a cast the compiler might emit an warning about using
> +     sizeof on a struct (where the builtin returns the pointer size).  */
> +  return INLINE_SYSCALL (utimensat, 4, fd, NULL, (const struct timespec*)tsp,
> +			 0);
>  #else
>    __set_errno (ENOSYS);
>    return -1;
> diff --git a/sysdeps/unix/sysv/linux/futimesat.c b/sysdeps/unix/sysv/linux/futimesat.c
> index ac96e2a..f7d5645 100644
> --- a/sysdeps/unix/sysv/linux/futimesat.c
> +++ b/sysdeps/unix/sysv/linux/futimesat.c
> @@ -28,13 +28,13 @@
>  /* Change the access time of FILE relative to FD to TVP[0] and
>     the modification time of FILE to TVP[1].  */
>  int
> -futimesat (fd, file, tvp)
> -     int fd;
> -     const char *file;
> -     const struct timeval tvp[2];
> +futimesat (int fd, const char *file, const struct timeval tvp[2])
>  {
>    if (file == NULL)
>      return __futimes (fd, tvp);
>  
> -  return INLINE_SYSCALL (futimesat, 3, fd, file, tvp);
> +  /* Some archs (powerpc) add arguments type and size check using sizeof
> +     and without a cast the compiler might emit an warning about using
> +     sizeof on a struct (where the builtin returns the pointer size).  */
> +  return INLINE_SYSCALL (futimesat, 3, fd, file, (const struct timeval*)tvp);

I think it'd be better to just change the function parameter to const
struct timeval *tvp; the warning is meant to detect a case when a sizeof
is applied to a function parameter declared as an array.

	Marek


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