diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index 357d711978b3784ae64d8bc586176022234e5b32..a89fbd621a5632b8ca733156f5f59775c1db8c3a 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -918,6 +918,11 @@ bool Expr::isIntegerConstantExpr(llvm::APSInt &Result, ASTContext &Ctx,
     if (!SubExpr->getType()->isArithmeticType() ||
         !getType()->isIntegerType()) {
       if (Loc) *Loc = SubExpr->getLocStart();
+      // GCC accepts pointers as an extension.
+      // FIXME: check getLangOptions().NoExtensions. At the moment, it doesn't
+      // appear possible to get langOptions() from the Expr.
+      if (SubExpr->getType()->isPointerType()) // && !NoExtensions
+        return true;
       return false;
     }
 
diff --git a/clang/test/Sema/darwin-align-cast.c b/clang/test/Sema/darwin-align-cast.c
new file mode 100644
index 0000000000000000000000000000000000000000..adf938f29bc138b145b02d4e0f6a6bb4742ee685
--- /dev/null
+++ b/clang/test/Sema/darwin-align-cast.c
@@ -0,0 +1,23 @@
+// RUN: clang -fsyntax-only -verify %s
+typedef long unsigned int __darwin_size_t;
+typedef long __darwin_ssize_t;
+typedef __darwin_size_t size_t;
+typedef __darwin_ssize_t ssize_t;
+
+struct cmsghdr {};
+
+#if 0
+This code below comes from the following system headers:
+sys/socket.h:#define	CMSG_SPACE(l)		(__DARWIN_ALIGN(sizeof(struct  
+cmsghdr)) + __DARWIN_ALIGN(l))
+
+i386/_param.h:#define	__DARWIN_ALIGN(p)	((__darwin_size_t)((char *)(p)  
++ __DARWIN_ALIGNBYTES) &~ __DARWIN_ALIGNBYTES)
+#endif
+
+ssize_t sendFileDescriptor(int fd, void *data, size_t nbytes, int sendfd) {
+  union {
+    char control[(((__darwin_size_t)((char *)(sizeof(struct cmsghdr)) + (sizeof(__darwin_size_t) - 1)) &~ (sizeof(__darwin_size_t) - 1)) + ((__darwin_size_t)((char *)(sizeof(int)) + (sizeof(__darwin_size_t) - 1)) &~ (sizeof(__darwin_size_t) - 1)))];
+  } control_un;
+}
+