In C++, if the user redeclares a builtin function with a type that is

inconsistent with the type that the builtin *should* have, forget
about the builtin altogether: we don't want subsequence analyses,
CodeGen, etc., to think that we have a proper builtin function.

C is protected from errors here because it allows one to use a
library builtin without having a declaration, and detects inconsistent
(re-)declarations of builtins during declaration merging. C++ was
unprotected, and therefore would crash.

Fixes PR8839.

llvm-svn: 122351

1 files changed, 9 insertions, 0 deletions

diff --git a/clang/test/CodeGenCXX/builtins.cpp b/clang/test/CodeGenCXX/builtins.cpp
new file mode 100644
index 00000000000..0629c31015c
--- /dev/null
+++ b/clang/test/CodeGenCXX/builtins.cpp
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -emit-llvm -o - %s | FileCheck %s
+
+// PR8839
+extern "C" char memmove();
+
+int main() {
+  // CHECK: call signext i8 @memmove()
+  return memmove();
+}