[COFF] Improve correctness of def parsing for GNU features

The operator == used for exporting a function with a different
name in the DLL compared to the name in the import library
(which is useful for adding linker level aliases for function
in the import library) is a feature distinct and different from
the operator = used for exporting a function with a different
name (both in import library and DLL) than in the implementation
producing the DLL.

When creating an import library using dlltool, from a def file that
contains forwards (Func = OtherDll.Func), this shouldn't affect the
produced import library, which should still behave just as if it
was a normal exported function.

This clears a lot of confusion and subtle misunderstandings, and
avoids a parameter that was used to avoid creating weak aliases
when invoked from lld. (This parameter was added previously due to
the existing conflation of the two features.)

Differential Revision: https://reviews.llvm.org/D46245

llvm-svn: 331859

1 files changed, 7 insertions, 8 deletions

diff --git a/llvm/lib/Object/COFFImportFile.cpp b/llvm/lib/Object/COFFImportFile.cpp
index c249a6d97b4..4bde1db3078 100644
--- a/llvm/lib/Object/COFFImportFile.cpp
+++ b/llvm/lib/Object/COFFImportFile.cpp
@@ -566,8 +566,7 @@ NewArchiveMember ObjectFactory::createWeakExternal(StringRef Sym,
 
 Error writeImportLibrary(StringRef ImportName, StringRef Path,
                          ArrayRef<COFFShortExport> Exports,
-                         MachineTypes Machine, bool MakeWeakAliases,
-                         bool MinGW) {
+                         MachineTypes Machine, bool MinGW) {
 
   std::vector<NewArchiveMember> Members;
   ObjectFactory OF(llvm::sys::path::filename(ImportName), Machine);
@@ -585,12 +584,6 @@ Error writeImportLibrary(StringRef ImportName, StringRef Path,
     if (E.Private)
       continue;
 
-    if (E.isWeak() && MakeWeakAliases) {
-      Members.push_back(OF.createWeakExternal(E.Name, E.ExtName, false));
-      Members.push_back(OF.createWeakExternal(E.Name, E.ExtName, true));
-      continue;
-    }
-
     ImportType ImportType = IMPORT_CODE;
     if (E.Data)
       ImportType = IMPORT_DATA;
@@ -606,6 +599,12 @@ Error writeImportLibrary(StringRef ImportName, StringRef Path,
     if (!Name)
       return Name.takeError();
 
+    if (!E.AliasTarget.empty() && *Name != E.AliasTarget) {
+      Members.push_back(OF.createWeakExternal(E.AliasTarget, *Name, false));
+      Members.push_back(OF.createWeakExternal(E.AliasTarget, *Name, true));
+      continue;
+    }
+
     Members.push_back(
         OF.createShortImport(*Name, E.Ordinal, ImportType, NameType));
   }