Be more careful in applying pragma weak. Fixes pr14974.

GCC applies a pragma weak to a decl if it matches the mangled name. We used
to apply if it matched the plain name.

This patch is a compromise: we apply the pragma only if it matches the name
and the decl has C language linkage.

llvm-svn: 176110

1 files changed, 31 insertions, 0 deletions

diff --git a/clang/test/CodeGenCXX/pragma-weak.cpp b/clang/test/CodeGenCXX/pragma-weak.cpp
new file mode 100644
index 00000000000..ed537ffcd29
--- /dev/null
+++ b/clang/test/CodeGenCXX/pragma-weak.cpp
@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 -emit-llvm %s -o - | FileCheck %s
+
+#pragma weak zex
+int zex;
+// GCC produces a weak symbol for this because it matches mangled names.
+// Different c++ ABIs may or may not mangle this, so we produce a strong
+// symbol.
+// CHECK: @zex = global i32
+
+#pragma weak foo
+struct S {  void foo(); };
+void S::foo() {}
+// CHECK: define void @_ZN1S3fooEv(
+
+#pragma weak zed
+namespace bar {  void zed() {} }
+// CHECK: define void @_ZN3bar3zedEv(
+
+#pragma weak bah
+void bah() {}
+// CHECK: define void @_Z3bahv(
+
+#pragma weak baz
+extern "C" void baz() {}
+// CHECK: define weak void @baz(
+
+#pragma weak _Z3baxv
+void bax() {}
+// GCC produces a weak symbol for this one, but it doesn't look like a good
+// idea to expose the mangling to the pragma unless we really have to.
+// CHECK: define void @_Z3baxv(