Re: [PATCH] Avoid one "parameter unused" warnings.

[Eric Blake]

On 01/01/2018 03:53 AM, Paul Eggert wrote:
> Thanks, but -Wunused-parameter issues so many false alarms that I think
> I'd rather just ask people to compile with -Wno-unused-parameter. That's
> what coreutils does, and Emacs, and so forth.
> 
> By the way, this thread duplicates one of a couple of days ago, starting
> here:
> 
> http://lists.gnu.org/archive/html/bug-gnulib/2017-12/msg00077.html
> 
> Is there some new project using Gnulib that is causing these new
> messages? If so, perhaps I should propose a patch to it to pacify GCC
> without having to pollute the code with void no-op casts.

Note that this patch is copying the style that is already present in
get_stat_birthtime_ns(), so on that grounds, I'd argue that we WANT the
patch for consistency.  But why not use _GL_UNUSED instead of
cast-to-void (after all, gcc does NOT warn if you mark something with
_GL_UNUSED but then actually use it; precisely because of situations
where the use is conditional based on #if)?  As in:

diff --git i/lib/stat-time.h w/lib/stat-time.h
index 5f8bf4e12..104f53766 100644
--- i/lib/stat-time.h
+++ w/lib/stat-time.h
@@ -102,15 +102,13 @@ get_stat_mtime_ns (struct stat const *st)

 /* Return the nanosecond component of *ST's birth time.  */
 _GL_STAT_TIME_INLINE long int _GL_ATTRIBUTE_PURE
-get_stat_birthtime_ns (struct stat const *st)
+get_stat_birthtime_ns (struct stat const *st _GL_UNUSED)
 {
 # if defined HAVE_STRUCT_STAT_ST_BIRTHTIMESPEC_TV_NSEC
   return STAT_TIMESPEC (st, st_birthtim).tv_nsec;
 # elif defined HAVE_STRUCT_STAT_ST_BIRTHTIMENSEC
   return STAT_TIMESPEC_NS (st, st_birthtim);
 # else
-  /* Avoid a "parameter unused" warning.  */
-  (void) st;
   return 0;
 # endif
 }
@@ -160,7 +158,7 @@ get_stat_mtime (struct stat const *st)
 /* Return *ST's birth time, if available; otherwise return a value
    with tv_sec and tv_nsec both equal to -1.  */
 _GL_STAT_TIME_INLINE struct timespec _GL_ATTRIBUTE_PURE
-get_stat_birthtime (struct stat const *st)
+get_stat_birthtime (struct stat const *st _GL_UNUSED)
 {
   struct timespec t;

@@ -184,8 +182,6 @@ get_stat_birthtime (struct stat const *st)
   /* Birth time is not supported.  */
   t.tv_sec = -1;
   t.tv_nsec = -1;
-  /* Avoid a "parameter unused" warning.  */
-  (void) st;
 #endif

 #if (defined HAVE_STRUCT_STAT_ST_BIRTHTIMESPEC_TV_NSEC \
@@ -212,7 +208,7 @@ get_stat_birthtime (struct stat const *st)
    errno to EOVERFLOW if normalization overflowed.  This function
    is intended to be private to this .h file.  */
 _GL_STAT_TIME_INLINE int
-stat_time_normalize (int result, struct stat *st)
+stat_time_normalize (int result, struct stat *st _GL_UNUSED)
 {
 #if defined __sun && defined STAT_TIMESPEC
   if (result == 0)


-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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