Index: base/template_util.h |
diff --git a/base/template_util.h b/base/template_util.h |
index 74c8e5afdc63dfb63f25922fc62835d854a8d48b..98506f029dee2f22a31fba0d2999b8de33cd72d3 100644 |
--- a/base/template_util.h |
+++ b/base/template_util.h |
@@ -6,6 +6,7 @@ |
#define BASE_TEMPLATE_UTIL_H_ |
#include <stddef.h> |
+#include <iosfwd> |
#include <type_traits> |
#include <utility> |
@@ -57,6 +58,15 @@ struct IsAssignableImpl |
template <class Lvalue, class Rvalue> |
struct IsAssignableImpl<Lvalue, Rvalue, true> : public std::false_type {}; |
+// Uses expression SFINAE to detect whether using operator<< would work. |
+template <typename T, typename = void> |
+struct SupportsOstreamOperator : std::false_type {}; |
+template <typename T> |
+struct SupportsOstreamOperator<T, |
+ decltype(void(std::declval<std::ostream&>() |
+ << std::declval<T>()))> |
+ : std::true_type {}; |
+ |
} // namespace internal |
// TODO(crbug.com/554293): Remove this when all platforms have this in the std |
@@ -82,6 +92,26 @@ struct is_move_assignable |
const typename std::add_rvalue_reference<T>::type> { |
}; |
+// underlying_type produces the integer type backing an enum type. |
+// This hacks around libstdc++ 4.6 missing std::underlying_type, while we need |
+// to support it. |
+// TODO(crbug.com/554293): Remove this when all platforms have this in the std |
+// namespace. |
+#define CR_GLIBCXX_4_7_0 20120322 |
+#define CR_GLIBCXX_4_5_4 20120702 |
+#define CR_GLIBCXX_4_6_4 20121127 |
+#if defined(__GLIBCXX__) && \ |
+ (__GLIBCXX__ < CR_GLIBCXX_4_7_0 || __GLIBCXX__ == CR_GLIBCXX_4_5_4 || \ |
+ __GLIBCXX__ == CR_GLIBCXX_4_6_4) |
+template <typename T> |
+struct underlying_type { |
+ using type = __underlying_type(T); |
+}; |
+#else |
+template <typename T> |
+using underlying_type = std::underlying_type<T>; |
+#endif |
+ |
} // namespace base |
#endif // BASE_TEMPLATE_UTIL_H_ |