[libcxx] r203070 - Do not derive __gnu_cxx::hash<T> from std::hash<T>.
Peter Collingbourne
peter at pcc.me.uk
Wed Mar 5 20:11:11 PST 2014
Author: pcc
Date: Wed Mar 5 22:11:10 2014
New Revision: 203070
URL: http://llvm.org/viewvc/llvm-project?rev=203070&view=rev
Log:
Do not derive __gnu_cxx::hash<T> from std::hash<T>.
Instead, define explicit specializations for the basic types listed in
the SGI documentation. This solves two problems:
1) Helps avoid silent ODR violations caused by the absence of a
user-supplied __gnu_cxx::hash specialization in cases where a std::hash
specialization exists (e.g. for std::string).
2) __gnu_cxx::hash semantics are slightly different to those of
std::hash (for example, the former may dereference a pointer argument)
so it is inappropriate for __gnu_cxx::hash to receive std::hash
specializations by default.
Differential Revision: http://llvm-reviews.chandlerc.com/D2747
Added:
libcxx/trunk/test/extensions/hash/
libcxx/trunk/test/extensions/hash/specializations.fail.cpp
libcxx/trunk/test/extensions/hash/specializations.pass.cpp
libcxx/trunk/test/extensions/nothing_to_do.pass.cpp
Modified:
libcxx/trunk/include/ext/__hash
Modified: libcxx/trunk/include/ext/__hash
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/ext/__hash?rev=203070&r1=203069&r2=203070&view=diff
==============================================================================
--- libcxx/trunk/include/ext/__hash (original)
+++ libcxx/trunk/include/ext/__hash Wed Mar 5 22:11:10 2014
@@ -19,8 +19,7 @@
namespace __gnu_cxx {
using namespace std;
-template <typename _Tp> struct _LIBCPP_TYPE_VIS_ONLY hash : public std::hash<_Tp>
- { };
+template <typename _Tp> struct _LIBCPP_TYPE_VIS_ONLY hash { };
template <> struct _LIBCPP_TYPE_VIS_ONLY hash<const char*>
: public unary_function<const char*, size_t>
@@ -41,6 +40,96 @@ template <> struct _LIBCPP_TYPE_VIS_ONLY
return __do_string_hash<const char *>(__c, __c + strlen(__c));
}
};
+
+template <> struct _LIBCPP_TYPE_VIS_ONLY hash<char>
+ : public unary_function<char, size_t>
+{
+ _LIBCPP_INLINE_VISIBILITY
+ size_t operator()(char __c) const _NOEXCEPT
+ {
+ return __c;
+ }
+};
+
+template <> struct _LIBCPP_TYPE_VIS_ONLY hash<signed char>
+ : public unary_function<signed char, size_t>
+{
+ _LIBCPP_INLINE_VISIBILITY
+ size_t operator()(signed char __c) const _NOEXCEPT
+ {
+ return __c;
+ }
+};
+
+template <> struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned char>
+ : public unary_function<unsigned char, size_t>
+{
+ _LIBCPP_INLINE_VISIBILITY
+ size_t operator()(unsigned char __c) const _NOEXCEPT
+ {
+ return __c;
+ }
+};
+
+template <> struct _LIBCPP_TYPE_VIS_ONLY hash<short>
+ : public unary_function<short, size_t>
+{
+ _LIBCPP_INLINE_VISIBILITY
+ size_t operator()(short __c) const _NOEXCEPT
+ {
+ return __c;
+ }
+};
+
+template <> struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned short>
+ : public unary_function<unsigned short, size_t>
+{
+ _LIBCPP_INLINE_VISIBILITY
+ size_t operator()(unsigned short __c) const _NOEXCEPT
+ {
+ return __c;
+ }
+};
+
+template <> struct _LIBCPP_TYPE_VIS_ONLY hash<int>
+ : public unary_function<int, size_t>
+{
+ _LIBCPP_INLINE_VISIBILITY
+ size_t operator()(int __c) const _NOEXCEPT
+ {
+ return __c;
+ }
+};
+
+template <> struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned int>
+ : public unary_function<unsigned int, size_t>
+{
+ _LIBCPP_INLINE_VISIBILITY
+ size_t operator()(unsigned int __c) const _NOEXCEPT
+ {
+ return __c;
+ }
+};
+
+template <> struct _LIBCPP_TYPE_VIS_ONLY hash<long>
+ : public unary_function<long, size_t>
+{
+ _LIBCPP_INLINE_VISIBILITY
+ size_t operator()(long __c) const _NOEXCEPT
+ {
+ return __c;
+ }
+};
+
+template <> struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned long>
+ : public unary_function<unsigned long, size_t>
+{
+ _LIBCPP_INLINE_VISIBILITY
+ size_t operator()(unsigned long __c) const _NOEXCEPT
+ {
+ return __c;
+ }
+};
}
#endif // _LIBCPP_EXT_HASH
Added: libcxx/trunk/test/extensions/hash/specializations.fail.cpp
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/test/extensions/hash/specializations.fail.cpp?rev=203070&view=auto
==============================================================================
--- libcxx/trunk/test/extensions/hash/specializations.fail.cpp (added)
+++ libcxx/trunk/test/extensions/hash/specializations.fail.cpp Wed Mar 5 22:11:10 2014
@@ -0,0 +1,17 @@
+//===----------------------------------------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include <assert.h>
+#include <ext/hash_map>
+#include <string>
+
+int main()
+{
+ assert(__gnu_cxx::hash<std::string>()(std::string()) == 0); // error
+}
Added: libcxx/trunk/test/extensions/hash/specializations.pass.cpp
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/test/extensions/hash/specializations.pass.cpp?rev=203070&view=auto
==============================================================================
--- libcxx/trunk/test/extensions/hash/specializations.pass.cpp (added)
+++ libcxx/trunk/test/extensions/hash/specializations.pass.cpp Wed Mar 5 22:11:10 2014
@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include <assert.h>
+#include <ext/hash_map>
+#include <string>
+
+int main()
+{
+ char str[] = "test";
+ assert(__gnu_cxx::hash<const char *>()("test") ==
+ std::hash<std::string>()("test"));
+ assert(__gnu_cxx::hash<char *>()(str) == std::hash<std::string>()("test"));
+ assert(__gnu_cxx::hash<char>()(42) == 42);
+ assert(__gnu_cxx::hash<signed char>()(42) == 42);
+ assert(__gnu_cxx::hash<unsigned char>()(42) == 42);
+ assert(__gnu_cxx::hash<short>()(42) == 42);
+ assert(__gnu_cxx::hash<unsigned short>()(42) == 42);
+ assert(__gnu_cxx::hash<int>()(42) == 42);
+ assert(__gnu_cxx::hash<unsigned int>()(42) == 42);
+ assert(__gnu_cxx::hash<long>()(42) == 42);
+ assert(__gnu_cxx::hash<unsigned long>()(42) == 42);
+}
Added: libcxx/trunk/test/extensions/nothing_to_do.pass.cpp
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/test/extensions/nothing_to_do.pass.cpp?rev=203070&view=auto
==============================================================================
--- libcxx/trunk/test/extensions/nothing_to_do.pass.cpp (added)
+++ libcxx/trunk/test/extensions/nothing_to_do.pass.cpp Wed Mar 5 22:11:10 2014
@@ -0,0 +1,12 @@
+//===----------------------------------------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+int main()
+{
+}
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