From a35de714e1c813415f11c9fb4fcede07d16c7f92 Mon Sep 17 00:00:00 2001
From: Martin Nolte <mnolte@dune-project.org>
Date: Sat, 22 Sep 2012 07:57:10 +0000
Subject: [PATCH] only use std::integral_constant, if it conforms to the C++11
standard
C++11 requires a cast operator from integral_constant< T, v > to T. As far as I
could make out, no gcc version provides this cast in <tr1/type_traits> and only
gcc >= 4.6 provides it in <type_traits>. Therefore, the configure check now tests
for the cast operator only in <type_traits>.
Note: Our drop-in replacement conforms to the standard in the above-mentioned
sense.
[[Imported from SVN: r6992]]
---
dune/common/typetraits.hh | 10 +++-------
m4/dune_tr1_headers.m4 | 17 +++++++++++++++++
2 files changed, 20 insertions(+), 7 deletions(-)
diff --git a/dune/common/typetraits.hh b/dune/common/typetraits.hh
index 40c1f67f2..561086be6 100644
--- a/dune/common/typetraits.hh
+++ b/dune/common/typetraits.hh
@@ -395,15 +395,11 @@ namespace Dune
//
// integral_constant (C++0x 20.7.3 "Helper classes")
//
-#if defined HAVE_TYPE_TRAITS
+#if HAVE_INTEGRAL_CONSTANT
using std::integral_constant;
using std::true_type;
using std::false_type;
-#elif defined HAVE_TR1_TYPE_TRAITS
- using std::tr1::integral_constant;
- using std::tr1::true_type;
- using std::tr1::false_type;
-#else
+#else // #if HAVE_INTEGRAL_CONSTANT
//! Generate a type for a given integral constant
/**
* \tparam T Type of the constant.
@@ -425,7 +421,7 @@ namespace Dune
typedef integral_constant<bool, true> true_type;
//! type for false
typedef integral_constant<bool, false> false_type;
-#endif
+#endif // #else // #if HAVE_INTEGRAL_CONSTANT
/** @} */
}
diff --git a/m4/dune_tr1_headers.m4 b/m4/dune_tr1_headers.m4
index ec04516ce..d9a0807aa 100644
--- a/m4/dune_tr1_headers.m4
+++ b/m4/dune_tr1_headers.m4
@@ -20,6 +20,23 @@ AC_DEFUN([DUNE_TR1_HEADERS], [
AS_IF([test "x$dune_cv_array_cplusplus0x" != "xno"],
[AC_DEFINE([HAVE_ARRAY], 1, [Define to 1 if the <array> C++0x is available and support array::fill])
])
+ AC_CACHE_CHECK([whether integral_constant conforming to C++11 is supported], dune_cv_integral_constant_cplusplus11, [
+ AC_COMPILE_IFELSE([
+ AC_LANG_PROGRAM([
+ #include <type_traits>
+ void f( int );
+ ],[
+ f( std::integral_constant< int, 42 >() );
+ ])
+ ],[
+ dune_cv_integral_constant_cplusplus11=yes
+ ],[
+ dune_cv_integral_constant_cplusplus11=no
+ ])
+ ])
+ AS_IF([test "x$dune_cv_integral_constant_cplusplus11" != "xno"],[
+ AC_DEFINE([HAVE_INTEGRAL_CONSTANT], 1, [Define to 1 if std::integral_constant< T, v > is supported and casts into T])
+ ])
])
AC_LANG_POP([C++])
])
--
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