[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, 11 insertions, 2 deletions

diff --git a/llvm/lib/Object/COFFModuleDefinition.cpp b/llvm/lib/Object/COFFModuleDefinition.cpp
index a571354648d..c703071b86e 100644
--- a/llvm/lib/Object/COFFModuleDefinition.cpp
+++ b/llvm/lib/Object/COFFModuleDefinition.cpp
@@ -37,6 +37,7 @@ enum Kind {
   Identifier,
   Comma,
   Equal,
+  EqualEqual,
   KwBase,
   KwConstant,
   KwData,
@@ -104,9 +105,10 @@ public:
     }
     case '=':
       Buf = Buf.drop_front();
-      // GNU dlltool accepts both = and ==.
-      if (Buf.startswith("="))
+      if (Buf.startswith("=")) {
         Buf = Buf.drop_front();
+        return Token(EqualEqual, "==");
+      }
       return Token(Equal, "=");
     case ',':
       Buf = Buf.drop_front();
@@ -282,6 +284,13 @@ private:
         E.Private = true;
         continue;
       }
+      if (Tok.K == EqualEqual) {
+        read();
+        E.AliasTarget = Tok.Value;
+        if (Machine == IMAGE_FILE_MACHINE_I386 && !isDecorated(E.AliasTarget, MingwDef))
+          E.AliasTarget = std::string("_").append(E.AliasTarget);
+        continue;
+      }
       unget();
       Info.Exports.push_back(E);
       return Error::success();