Add regression test for maybeMangle issue

This was crbug.com/1222724, which caused D104529 to be reverted. The
new test fails when D104529 is reapplied locally.

diff --git a/lld/test/COFF/def-export-cpp.s b/lld/test/COFF/def-export-cpp.s
new file mode 100644 (file)
index 0000000..e00b35b
--- /dev/null
+++ b/lld/test/COFF/def-export-cpp.s
@@ -0,0 +1,36 @@
+# REQUIRES: x86
+# RUN: split-file %s %t
+# RUN: llvm-mc -filetype=obj -triple=x86_64-windows-msvc %t/dllmain.s -o %t/dllmain.obj
+# RUN: llvm-mc -filetype=obj -triple=x86_64-windows-msvc %t/path.s -o %t/path.obj
+# RUN: lld-link -lib %t/dllmain.obj -out:%t/archive.lib
+# RUN: echo -e "LIBRARY foo\nEXPORTS\n  GetPathOnDisk" > %t.def
+# RUN: lld-link -entry:dllmain -dll -def:%t.def %t/path.obj %t/archive.lib -out:%t/foo.dll -implib:%t/foo.lib
+# RUN: llvm-readobj %t/foo.lib | FileCheck -check-prefix IMPLIB %s
+# RUN: llvm-readobj --coff-exports %t/foo.dll | FileCheck -check-prefix EXPORTS %s
+
+# IMPLIB: File: foo.dll
+# IMPLIB: Name type: undecorate
+# IMPLIB-NEXT: Symbol: __imp_?GetPathOnDisk@@YA_NPEA_W@Z
+# IMPLIB-NEXT: Symbol: ?GetPathOnDisk@@YA_NPEA_W@Z
+
+# EXPORTS: Name: GetPathOnDisk
+
+#--- path.s
+
+        .def    "?GetPathOnDisk@@YA_NPEA_W@Z";
+        .scl    2;
+        .type   32;
+        .endef
+        .globl  "?GetPathOnDisk@@YA_NPEA_W@Z"
+"?GetPathOnDisk@@YA_NPEA_W@Z":
+        retq
+
+#--- dllmain.s
+
+        .def     dllmain;
+        .scl    2;
+        .type   32;
+        .endef
+        .globl  dllmain
+dllmain:
+        retq