[PATCH] utimecmp: avoid new warning from upcoming gcc-4.5.0

[Jim Meyering]

This new warning is debatable:

  utimecmp.c: In function 'utimecmp':
  utimecmp.c:222:36: error: comparison between 'enum <anonymous>' and 'enum 
<anonymous>' [-Wenum-compare]

The code in question:

    enum { BILLION = 1000 * 1000 * 1000 };

    /* Best possible resolution that utimens can set and stat can return,
       due to system-call limitations.  It must be a power of 10 that is
       no greater than 1 billion.  */
    #if HAVE_UTIMENSAT
    enum { SYSCALL_RESOLUTION = 1 };
    #elif ((HAVE_FUTIMESAT || HAVE_WORKING_UTIMES)                  \
           && (defined HAVE_STRUCT_STAT_ST_ATIM_TV_NSEC             \
               || defined HAVE_STRUCT_STAT_ST_ATIMESPEC_TV_NSEC     \
               || defined HAVE_STRUCT_STAT_ST_ATIMENSEC             \
               || defined HAVE_STRUCT_STAT_ST_ATIM_ST__TIM_TV_NSEC  \
               || defined HAVE_STRUCT_STAT_ST_SPARE1))
    enum { SYSCALL_RESOLUTION = 1000 };
    #else
    enum { SYSCALL_RESOLUTION = BILLION };
    #endif

and here's line 222:

            if (SYSCALL_RESOLUTION == BILLION)

In general I use "enum"s for constants like this, so that defined symbols
are accessible in the debugger, but "BILLION" is pretty obvious here,
so I prefer to compromise its definition in gnulib, rather than to
require each utimecmp-using package (with a strict, non-warning policy)
to do something like the following patch, which I wrote but am not going
to use in coreutils.

So I've pushed this.

>From 56a9c0c14e067f5375863981337056a31e45c8f0 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Mon, 11 Jan 2010 16:50:02 +0100
Subject: [PATCH] utimecmp: avoid new warning from upcoming gcc-4.5.0

* lib/utimecmp.c (BILLION): Define using #define rather than an
anonymous enum, to placate upcoming gcc-4.5.0's -Wenum-compare.
---
 ChangeLog      |    6 ++++++
 lib/utimecmp.c |    2 +-
 2 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 291b88b..d075b31 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2010-01-11  Jim Meyering  <address@hidden>
+
+       utimecmp: avoid new warning from upcoming gcc-4.5.0
+       * lib/utimecmp.c (BILLION): Define using #define rather than an
+       anonymous enum, to placate upcoming gcc-4.5.0's -Wenum-compare.
+
 2010-01-11  Eric Blake  <address@hidden>

        math: add portability warnings for classification macros
diff --git a/lib/utimecmp.c b/lib/utimecmp.c
index 81c36b3..63a0c9a 100644
--- a/lib/utimecmp.c
+++ b/lib/utimecmp.c
@@ -39,7 +39,7 @@
 # define MAX(a, b) ((a) > (b) ? (a) : (b))
 #endif

-enum { BILLION = 1000 * 1000 * 1000 };
+#define BILLION (1000 * 1000 * 1000)

 /* Best possible resolution that utimens can set and stat can return,
    due to system-call limitations.  It must be a power of 10 that is
--
1.6.6.439.gaf68f



>From 77c4d350e18e48214431f321c0d3e598bb0327af Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Mon, 11 Jan 2010 16:29:26 +0100
Subject: [PATCH] build: avoid a warning in gnulib from experimental gcc-4.5.0

* configure.ac (GNULIB_WARN_CFLAGS): Remove -Wenum-compare,
to avoid a warning that is new in 4.5.0 20100109.
---
 configure.ac |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/configure.ac b/configure.ac
index b07a52b..4c35c02 100644
--- a/configure.ac
+++ b/configure.ac
@@ -122,6 +122,11 @@ if test "$gl_gcc_warnings" = yes; then
   nw="$nw -Wunused-macros"
   nw="$nw -Wmissing-prototypes"
   nw="$nw -Wold-style-definition"
+
+  # The sole violation is in utimecmp.c:222, but it doesn't seem to
+  # merit the warning or a fix.
+  gl_WARN_ADD([-Wno-enum-compare])
+
   gl_MANYWARN_COMPLEMENT([GNULIB_WARN_CFLAGS], [$WARN_CFLAGS], [$nw])
   AC_SUBST([GNULIB_WARN_CFLAGS])
 fi
--
1.6.6.439.gaf68f