[LLD] [COFF] Fix the name type for stdcall functions in import libraries

[mstorsjo]

Summary

Since SVN r303491 and r304573, LLD used the COFFImportLibrary functions from LLVM. These only had two names, Name and ExtName, which wasn't enough to convey all the details of stdcall functions.

Stdcall functions got the wrong symbol name in the import library itself in r303491, which is why it was reverted in r304561. When re-landed and fixed in r304573 (after adding a test in r304572), the symbol name itself in the import library ended up right, but the name type of the import library entry was wrong.

This had the effect that linking to the import library succeeded (contrary to in r303491, where linking to such an import library failed), but at runtime, the symbol wouldn't be found in the DLL (since the caller linked to the stdcall decorated name).

[rnk]

lgtm

[mstorsjo]

Forgot to say explicitly, that this depends on D36544. This also fixes a regression since 4.0, where linking to import libraries with stdcall creates broken executables. So once done, this and D36544 should be backported to 5.0, ping @hans.

COFF/Driver.cpp

static std::string getImportName(bool AsLib) {
 
   return Out.str();
 }
 
 static void createImportLibrary(bool AsLib) {
   std::vector<COFFShortExport> Exports;
   for (Export &E1 : Config->Exports) {
     COFFShortExport E2;
-    // Use SymbolName, which will have any stdcall or fastcall qualifiers.
-    E2.Name = E1.SymbolName;
+    E2.Name = E1.Name;
+    E2.SymbolName = E1.SymbolName;
     E2.ExtName = E1.ExtName;
     E2.Ordinal = E1.Ordinal;
     E2.Noname = E1.Noname;
     E2.Data = E1.Data;
     E2.Private = E1.Private;
     E2.Constant = E1.Constant;
     Exports.push_back(E2);
   }

test/COFF/def-export-stdcall.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=i686-windows-msvc %s -o %t.obj
 # RUN: echo -e "LIBRARY foo\nEXPORTS\n  stdcall" > %t.def
 # RUN: lld-link -entry:dllmain -dll -def:%t.def %t.obj -out:%t.dll -implib:%t.lib
-# RUN: llvm-nm %t.lib | FileCheck %s
+# RUN: llvm-readobj %t.lib | FileCheck %s
+# CHECK: Name type: undecorate
 # CHECK: __imp__stdcall@8
 # CHECK: _stdcall@8
 
         .def     _stdcall@8;
         .scl    2;
         .type   32;
         .endef
         .globl  _stdcall@8