Simplify use of mode_t varargs.

diff --git a/ChangeLog b/ChangeLog
index 32f6c6b..a731f01 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,19 @@
+2009-05-21  Bruno Haible  <bruno@clisp.org>
+
+       Simplify use of mode_t varargs.
+       * lib/open.c (open): Use PROMOTED_MODE_T instead of a conditional that
+       uses 'mode_t' or 'int'.
+       * lib/openat.c (openat): Likewise.
+       * lib/open-safer.c (open_safer): Likewise.
+       * m4/mode_t.m4: New file.
+       * m4/open.m4 (gl_PREREQ_OPEN): Require gl_PROMOTED_TYPE_MODE_T.
+       * m4/openat.m4 (gl_PREREQ_OPENAT): Likewise.
+       * m4/fcntl-safer.m4 (gl_FCNTL_SAFER): Likewise.
+       * modules/open (Files): Add m4/mode_t.m4.
+       * modules/openat (Files): Likewise.
+       * modules/fcntl-safer (Files): Likewise.
+       Suggested by Eric Blake.
+
 2009-05-21  Pádraig Brady  <P@draigbrady.com>
 
        * doc/glibc-functions/fallocate.texi: New file.

diff --git a/lib/open-safer.c b/lib/open-safer.c
index 15bf6a6..48d558f 100644 (file)
--- a/lib/open-safer.c
+++ b/lib/open-safer.c
@@ -1,6 +1,6 @@
 /* Invoke open, but avoid some glitches.
 
-   Copyright (C) 2005, 2006, 2008 Free Software Foundation, Inc.
+   Copyright (C) 2005, 2006, 2008-2009 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -35,13 +35,9 @@ open_safer (char const *file, int flags, ...)
       va_list ap;
       va_start (ap, flags);
 
-      /* Assume mode_t promotes to int if and only if it is smaller.
-        This assumption isn't guaranteed by the C standard, but we
-        don't know of any real-world counterexamples.  */
-      if (sizeof (mode_t) < sizeof (int))
-       mode = va_arg (ap, int);
-      else
-       mode = va_arg (ap, mode_t);
+      /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
+        creates crashing code when 'mode_t' is smaller than 'int'.  */
+      mode = va_arg (ap, PROMOTED_MODE_T);
 
       va_end (ap);
     }

diff --git a/lib/open.c b/lib/open.c
index 13af274..326e6d1 100644 (file)
--- a/lib/open.c
+++ b/lib/open.c
@@ -1,5 +1,5 @@
 /* Open a descriptor to a file.
-   Copyright (C) 2007-2008 Free Software Foundation, Inc.
+   Copyright (C) 2007-2009 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -51,12 +51,9 @@ open (const char *filename, int flags, ...)
       va_list arg;
       va_start (arg, flags);
 
-      /* If mode_t is narrower than int, use the promoted type (int),
-        not mode_t.  Use sizeof to guess whether mode_t is narrower;
-        we don't know of any practical counterexamples.  */
-      mode = (sizeof (mode_t) < sizeof (int)
-             ? va_arg (arg, int)
-             : va_arg (arg, mode_t));
+      /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
+        creates crashing code when 'mode_t' is smaller than 'int'.  */
+      mode = va_arg (arg, PROMOTED_MODE_T);
 
       va_end (arg);
     }

diff --git a/lib/openat.c b/lib/openat.c
index 0c32672..77a85bf 100644 (file)
--- a/lib/openat.c
+++ b/lib/openat.c
@@ -1,5 +1,5 @@
 /* provide a replacement openat function
-   Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
+   Copyright (C) 2004-2009 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -47,12 +47,9 @@ openat (int fd, char const *file, int flags, ...)
       va_list arg;
       va_start (arg, flags);
 
-      /* If mode_t is narrower than int, use the promoted type (int),
-         not mode_t.  Use sizeof to guess whether mode_t is narrower;
-         we don't know of any practical counterexamples.  */
-      mode = (sizeof (mode_t) < sizeof (int)
-             ? va_arg (arg, int)
-             : va_arg (arg, mode_t));
+      /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
+        creates crashing code when 'mode_t' is smaller than 'int'.  */
+      mode = va_arg (arg, PROMOTED_MODE_T);
 
       va_end (arg);
     }

diff --git a/m4/fcntl-safer.m4 b/m4/fcntl-safer.m4
index 3475b0a..e2080df 100644 (file)
--- a/m4/fcntl-safer.m4
+++ b/m4/fcntl-safer.m4
@@ -1,5 +1,5 @@
-#serial 5
-dnl Copyright (C) 2005-2007 Free Software Foundation, Inc.
+#serial 6
+dnl Copyright (C) 2005-2007, 2009 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -8,4 +8,6 @@ AC_DEFUN([gl_FCNTL_SAFER],
 [
   AC_LIBOBJ([open-safer])
   AC_LIBOBJ([creat-safer])
+  # Prerequisites of lib/open-safer.c.
+  AC_REQUIRE([gl_PROMOTED_TYPE_MODE_T])
 ])

diff --git a/m4/mode_t.m4 b/m4/mode_t.m4
new file mode 100644 (file)
index 0000000..a4dd694
--- /dev/null
+++ b/m4/mode_t.m4
@@ -0,0 +1,26 @@
+# mode_t.m4 serial 1
+dnl Copyright (C) 2009 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+# For using mode_t, it's sufficient to use AC_TYPE_MODE_T and
+# include <sys/types.h>.
+
+# Define PROMOTED_MODE_T to the type that is the result of "default argument
+# promotion" (ISO C 6.5.2.2.(6)) of the type mode_t.
+AC_DEFUN([gl_PROMOTED_TYPE_MODE_T],
+[
+  AC_REQUIRE([AC_TYPE_MODE_T])
+  AC_CACHE_CHECK([for promoted mode_t type], [gl_cv_promoted_mode_t], [
+    dnl Assume mode_t promotes to 'int' if and only if it is smaller than 'int',
+    dnl and to itself otherwise. This assumption is not guaranteed by the ISO C
+    dnl standard, but we don't know of any real-world counterexamples.
+    AC_TRY_COMPILE([#include <sys/types.h>],
+      [typedef int array[2 * (sizeof (mode_t) < sizeof (int)) - 1];],
+      [gl_cv_promoted_mode_t='int'],
+      [gl_cv_promoted_mode_t='mode_t'])
+  ])
+  AC_DEFINE_UNQUOTED([PROMOTED_MODE_T], [$gl_cv_promoted_mode_t],
+    [Define to the type that is the result of default argument promotions of type mode_t.])
+])

diff --git a/m4/open.m4 b/m4/open.m4
index 6e286c9..3202886 100644 (file)
--- a/m4/open.m4
+++ b/m4/open.m4
@@ -1,4 +1,4 @@
-# open.m4 serial 5
+# open.m4 serial 6
 dnl Copyright (C) 2007-2009 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -62,5 +62,6 @@ AC_DEFUN([gl_REPLACE_OPEN],
 AC_DEFUN([gl_PREREQ_OPEN],
 [
   AC_REQUIRE([AC_C_INLINE])
+  AC_REQUIRE([gl_PROMOTED_TYPE_MODE_T])
   :
 ])

diff --git a/m4/openat.m4 b/m4/openat.m4
index 10eac5c..daa6a53 100644 (file)
--- a/m4/openat.m4
+++ b/m4/openat.m4
@@ -1,4 +1,4 @@
-# serial 17
+# serial 18
 # See if we need to use our replacement for Solaris' openat et al functions.
 
 dnl Copyright (C) 2004-2009 Free Software Foundation, Inc.
@@ -87,5 +87,6 @@ AC_DEFUN([gl_FUNC_FCHOWNAT],
 
 AC_DEFUN([gl_PREREQ_OPENAT],
 [
+  AC_REQUIRE([gl_PROMOTED_TYPE_MODE_T])
   :
 ])

diff --git a/modules/fcntl-safer b/modules/fcntl-safer
index 937b54f..253b76b 100644 (file)
--- a/modules/fcntl-safer
+++ b/modules/fcntl-safer
@@ -7,6 +7,7 @@ lib/creat-safer.c
 lib/fcntl-safer.h
 lib/open-safer.c
 m4/fcntl-safer.m4
+m4/mode_t.m4
 
 Depends-on:
 open

diff --git a/modules/open b/modules/open
index f792adf..e89efde 100644 (file)
--- a/modules/open
+++ b/modules/open
@@ -4,6 +4,7 @@ open() function: open a descriptor to a file.
 Files:
 lib/open.c
 m4/open.m4
+m4/mode_t.m4
 
 Depends-on:
 fcntl

diff --git a/modules/openat b/modules/openat
index f0c70b1..561687d 100644 (file)
--- a/modules/openat
+++ b/modules/openat
@@ -12,6 +12,7 @@ lib/openat.h
 lib/openat-priv.h
 lib/openat-proc.c
 m4/openat.m4
+m4/mode_t.m4
 
 Depends-on:
 dirname