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

[Marek Polacek <polacek at redhat dot com>]

On Tue, Jan 06, 2015 at 11:41:48AM -0200, Adhemerval Zanella wrote:
> On 06-01-2015 11:18, Marek Polacek wrote:
> > 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
> >
> I personally don't have a preference, this suggestion was given by Joseph in a
> previous threads requesting for comments.  I only see that pushing your suggestion
> will require more changes (the headers and manual).

Allright, in that case please watch for formatting,
(const struct timeval*)tvp
should be
(const struct timeval *) tvp

	Marek