Implement built-in macro '__has_warning', which allows one to query if a warning flag is valid. Fixes <rdar://problem/10263428>.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@141802 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/LanguageExtensions.html b/docs/LanguageExtensions.html
index d8a57df..ef57a65 100644
--- a/docs/LanguageExtensions.html
+++ b/docs/LanguageExtensions.html
@@ -300,6 +300,23 @@
file. A warning will also be issued if an absolute path
is used in the file argument.</p>
+
+<!-- ======================================================================= -->
+<h3><a name="__has_warning">__has_warning</a></h3>
+<!-- ======================================================================= -->
+
+<p>This function-like macro takes a string literal that represents a command
+ line option for a warning and returns true if that is a valid warning
+ option.</p>
+
+<blockquote>
+<pre>
+#if __has_warning("-Wformat")
+...
+#endif
+</pre>
+</blockquote>
+
<!-- ======================================================================= -->
<h2 id="builtinmacros">Builtin Macros</h2>
<!-- ======================================================================= -->