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authorGregor Jasny <gjasny@googlemail.com>2012-02-14 20:21:37 +0100
committerGregor Jasny <gjasny@googlemail.com>2012-02-14 20:31:09 +0100
commit5b0251d96b422e43666196c63405ec74c7860757 (patch)
tree0f348328d13880a83b36d5e833667c928543b7f3 /m4
parentcc9c1dfdf93e76bf466ded8c354b1585de31890f (diff)
libv4l: Check for correct mode_t promotion type at configure time
Signed-off-by: Gregor Jasny <gjasny@googlemail.com>
Diffstat (limited to 'm4')
-rw-r--r--m4/mode_t.m426
1 files changed, 26 insertions, 0 deletions
diff --git a/m4/mode_t.m4 b/m4/mode_t.m4
new file mode 100644
index 00000000..40f612a6
--- /dev/null
+++ b/m4/mode_t.m4
@@ -0,0 +1,26 @@
+# mode_t.m4 serial 2
+dnl Copyright (C) 2009-2012 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_COMPILE_IFELSE([AC_LANG_PROGRAM([[#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.])
+])

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