From afdf137c50f7f96ef865cf007f660dd663a8731f Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Thu, 3 Feb 2011 21:57:35 +0000
Subject: [PATCH] Add __has_feature() for each of the type traits

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@124820 91177308-0d34-0410-b5e6-96231b3b80d8
---
 docs/LanguageExtensions.html           | 43 +++++++++++-
 lib/Lex/PPMacroExpansion.cpp           | 19 ++++++
 test/Lexer/has_feature_type_traits.cpp | 91 ++++++++++++++++++++++++++
 3 files changed, 152 insertions(+), 1 deletion(-)
 create mode 100644 test/Lexer/has_feature_type_traits.cpp

diff --git a/docs/LanguageExtensions.html b/docs/LanguageExtensions.html
index 30c85ffcbd..8b6b96f6f2 100644
--- a/docs/LanguageExtensions.html
+++ b/docs/LanguageExtensions.html
@@ -46,13 +46,14 @@ td {
   <li><a href="#cxx_strong_enums">C++0x strongly-typed enumerations</a></li>
   <li><a href="#cxx_trailing_return">C++0x trailing return type</a></li>
   </ul>
+<li><a href="#checking_type_traits">Checks for Type Traits</a></li>
 <li><a href="#blocks">Blocks</a></li>
 <li><a href="#overloading-in-c">Function Overloading in C</a></li>
 <li><a href="#builtins">Builtin Functions</a>
   <ul>
   <li><a href="#__builtin_shufflevector">__builtin_shufflevector</a></li>
   <li><a href="#__builtin_unreachable">__builtin_unreachable</a></li>
-  </ul>
+ </ul>
 </li>
 <li><a href="#targetspecific">Target-Specific Extensions</a>
   <ul>
@@ -436,6 +437,46 @@ the alternate function declaration syntax with trailing return type is enabled.<
 <p>Use <tt>__has_feature(cxx_strong_enums)</tt> to determine if support for
 strongly typed, scoped enumerations is enabled.</p>
 
+<!-- ======================================================================= -->
+<h2 id="checking_type_traits">Checks for Type Traits</h2>
+<!-- ======================================================================= -->
+
+<p>Clang supports the <a hef="http://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html">GNU C++ type traits</a> and a subset of the <a href="http://msdn.microsoft.com/en-us/library/ms177194(v=VS.100).aspx">Microsoft Visual C++ Type traits</a>. For each supported type trait <code>__X</code>, <code>__has_feature(X)</code> indicates the presence of the type trait. For example:
+<blockquote>
+<pre>
+#if __has_feature(is_convertible_to)
+template&lt;typename From, typename To&gt;
+struct is_convertible_to {
+  static const bool value = __is_convertible_to(From, To);
+};
+#else
+// Emulate type trait
+#endif
+</pre>
+</blockquote>
+
+<p>The following type traits are supported by Clang:</p>
+<ul>
+  <li><code>__has_nothrow_assign</code> (GNU, Microsoft)</li>
+  <li><code>__has_nothrow_copy</code> (GNU, Microsoft)</li>
+  <li><code>__has_nothrow_constructor</code> (GNU, Microsoft)</li>
+  <li><code>__has_trivial_assign</code> (GNU, Microsoft)</li>
+  <li><code>__has_trivial_copy</code> (GNU, Microsoft)</li>
+  <li><code>__has_trivial_constructor</code> (GNU, Microsoft)</li>
+  <li><code>__has_trivial_destructor</code> (GNU, Microsoft)</li>
+  <li><code>__has_virtual_destructor</code> (GNU, Microsoft)</li>
+  <li><code>__is_abstract</code> (GNU, Microsoft)</li>
+  <li><code>__is_base_of</code> (GNU, Microsoft)</li>
+  <li><code>__is_class</code> (GNU, Microsoft)</li>
+  <li><code>__is_convertible_to</code> (Microsoft)</li>
+  <li><code>__is_empty</code> (GNU, Microsoft)</li>
+  <li><code>__is_enum</code> (GNU, Microsoft)</li>
+  <li><code>__is_pod</code> (GNU, Microsoft)</li>
+  <li><code>__is_polymorphic</code> (GNU, Microsoft)</li>
+  <li><code>__is_union</code> (GNU, Microsoft)</li>
+  <li><code>__is_literal(type)</code>: Determines whether the given type is a literal type</li>
+</ul>
+
 <!-- ======================================================================= -->
 <h2 id="blocks">Blocks</h2>
 <!-- ======================================================================= -->
diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index 5fb55159de..4a719cac6c 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -565,6 +565,25 @@ static bool HasFeature(const Preprocessor &PP, const IdentifierInfo *II) {
            .Case("cxx_static_assert", LangOpts.CPlusPlus0x)
            .Case("cxx_trailing_return", LangOpts.CPlusPlus0x)
            .Case("cxx_variadic_templates", LangOpts.CPlusPlus0x)
+           // Type traits
+           .Case("has_nothrow_assign", LangOpts.CPlusPlus)
+           .Case("has_nothrow_copy", LangOpts.CPlusPlus)
+           .Case("has_nothrow_constructor", LangOpts.CPlusPlus)
+           .Case("has_trivial_assign", LangOpts.CPlusPlus)
+           .Case("has_trivial_copy", LangOpts.CPlusPlus)
+           .Case("has_trivial_constructor", LangOpts.CPlusPlus)
+           .Case("has_trivial_destructor", LangOpts.CPlusPlus)
+           .Case("has_virtual_destructor", LangOpts.CPlusPlus)
+           .Case("is_abstract", LangOpts.CPlusPlus)
+           .Case("is_base_of", LangOpts.CPlusPlus)
+           .Case("is_class", LangOpts.CPlusPlus)
+           .Case("is_convertible_to", LangOpts.CPlusPlus)
+           .Case("is_empty", LangOpts.CPlusPlus)
+           .Case("is_enum", LangOpts.CPlusPlus)
+           .Case("is_pod", LangOpts.CPlusPlus)
+           .Case("is_polymorphic", LangOpts.CPlusPlus)
+           .Case("is_union", LangOpts.CPlusPlus)
+           .Case("is_literal", LangOpts.CPlusPlus)
            .Case("tls", PP.getTargetInfo().isTLSSupported())
            .Default(false);
 }
diff --git a/test/Lexer/has_feature_type_traits.cpp b/test/Lexer/has_feature_type_traits.cpp
new file mode 100644
index 0000000000..3cfc602be6
--- /dev/null
+++ b/test/Lexer/has_feature_type_traits.cpp
@@ -0,0 +1,91 @@
+// RUN: %clang_cc1 -E %s -o - | FileCheck %s
+
+#if __has_feature(has_nothrow_assign)
+int has_nothrow_assign();
+#endif
+// CHECK: int has_nothrow_assign();
+
+#if __has_feature(has_nothrow_copy)
+int has_nothrow_copy();
+#endif
+// CHECK: int has_nothrow_copy();
+
+#if __has_feature(has_nothrow_constructor)
+int has_nothrow_constructor();
+#endif
+// CHECK: int has_nothrow_constructor();
+
+#if __has_feature(has_trivial_assign)
+int has_trivial_assign();
+#endif
+// CHECK: int has_trivial_assign();
+
+#if __has_feature(has_trivial_copy)
+int has_trivial_copy();
+#endif
+// CHECK: int has_trivial_copy();
+
+#if __has_feature(has_trivial_constructor)
+int has_trivial_constructor();
+#endif
+// CHECK: int has_trivial_constructor();
+
+#if __has_feature(has_trivial_destructor)
+int has_trivial_destructor();
+#endif
+// CHECK: int has_trivial_destructor();
+
+#if __has_feature(has_virtual_destructor)
+int has_virtual_destructor();
+#endif
+// CHECK: int has_virtual_destructor();
+
+#if __has_feature(is_abstract)
+int is_abstract();
+#endif
+// CHECK: int is_abstract();
+
+#if __has_feature(is_base_of)
+int is_base_of();
+#endif
+// CHECK: int is_base_of();
+
+#if __has_feature(is_class)
+int is_class();
+#endif
+// CHECK: int is_class();
+
+#if __has_feature(is_convertible_to)
+int is_convertible_to();
+#endif
+// CHECK: int is_convertible_to();
+
+#if __has_feature(is_empty)
+int is_empty();
+#endif
+// CHECK: int is_empty();
+
+#if __has_feature(is_enum)
+int is_enum();
+#endif
+// CHECK: int is_enum();
+
+#if __has_feature(is_pod)
+int is_pod();
+#endif
+// CHECK: int is_pod();
+
+#if __has_feature(is_polymorphic)
+int is_polymorphic();
+#endif
+// CHECK: int is_polymorphic();
+
+#if __has_feature(is_union)
+int is_union();
+#endif
+// CHECK: int is_union();
+
+#if __has_feature(is_literal)
+int is_literal();
+#endif
+// CHECK: int is_literal();
-- 
2.50.1