Don't trap when passing non-POD arguments to variadic functions in MS-compatibility mode

Clang warns (treated as error by default, but still ignored in system headers)
when passing non-POD arguments to variadic functions, and generates a trap
instruction to crash the program if that code is ever run.

Unfortunately, MSVC happily generates code for such calls without a warning,
and there is code in system headers that use it.

This makes Clang not insert the trap instruction when in -fms-compatibility
mode, while still generating the warning/error message.

Differential Revision: http://reviews.llvm.org/D5492

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@218640 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 26 insertions, 0 deletions

diff --git a/test/CodeGenCXX/vararg-non-pod-ms-compat.cpp b/test/CodeGenCXX/vararg-non-pod-ms-compat.cpp
new file mode 100644
index 0000000000..da05c0b524
--- /dev/null
+++ b/test/CodeGenCXX/vararg-non-pod-ms-compat.cpp
@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -Wno-error=non-pod-varargs -triple i686-pc-win32 -fms-compatibility -emit-llvm -o - %s | FileCheck %s -check-prefix=X86 -check-prefix=CHECK
+// RUN: %clang_cc1 -Wno-error=non-pod-varargs -triple x86_64-pc-win32 -fms-compatibility -emit-llvm -o - %s | FileCheck %s -check-prefix=X64 -check-prefix=CHECK
+
+struct X {
+  X();
+  ~X();
+  int data;
+};
+
+void vararg(...);
+
+void test(X x) {
+  // CHECK-LABEL: define void @"\01?test@@YAXUX@@@Z"
+
+  // X86: %[[argmem:[^ ]*]] = alloca inalloca <{ %struct.X }>
+  // X86: call void (<{ %struct.X }>*, ...)* bitcast (void (...)* @"\01?vararg@@YAXZZ" to void (<{ %struct.X }>*, ...)*)(<{ %struct.X }>* inalloca %[[argmem]])
+
+  // X64: %[[valptr:[^ ]*]] = getelementptr %struct.X* %{{[^ ]*}}, i32 0, i32 0
+  // X64: %[[val:[^ ]*]] = load i32* %[[valptr]]
+  // X64: call void (...)* @"\01?vararg@@YAXZZ"(i32 %[[val]])
+
+  // CHECK-NOT: llvm.trap
+  vararg(x);
+  // CHECK: ret void
+}
+