[COFF] Adjust how we flag weak externals

This fixes PR36096.

Originally based on a patch by Martell Malone.

Differential Revision: https://reviews.llvm.org/D44357

llvm-svn: 337613

Author: mstorsjo

llvm/include/llvm/Object/COFF.h

@@ -276,6 +276,7 @@ struct coff_symbol_generic {
 };
 
 struct coff_aux_section_definition;
+struct coff_aux_weak_external;
 
 class COFFSymbolRef {
 public:
@@ -360,6 +361,13 @@ class COFFSymbolRef {
     return getAux<coff_aux_section_definition>();
   }
 
+  const coff_aux_weak_external *getWeakExternal() const {
+    if (!getNumberOfAuxSymbols() ||
+        getStorageClass() != COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL)
+      return nullptr;
+    return getAux<coff_aux_weak_external>();
+  }
+
   bool isAbsolute() const {
     return getSectionNumber() == -1;
   }

llvm/lib/Object/ArchiveWriter.cpp

@@ -294,8 +294,7 @@ static bool isArchiveSymbol(const object::BasicSymbolRef &S) {
     return false;
   if (!(Symflags & object::SymbolRef::SF_Global))
     return false;
-  if (Symflags & object::SymbolRef::SF_Undefined &&
-      !(Symflags & object::SymbolRef::SF_Indirect))
+  if (Symflags & object::SymbolRef::SF_Undefined)
     return false;
   return true;
 }

llvm/lib/Object/COFFObjectFile.cpp

@@ -217,10 +217,10 @@ uint32_t COFFObjectFile::getSymbolFlags(DataRefImpl Ref) const {
   if (Symb.isExternal() || Symb.isWeakExternal())
     Result |= SymbolRef::SF_Global;
 
-  if (Symb.isWeakExternal()) {
+  if (const coff_aux_weak_external *AWE = Symb.getWeakExternal()) {
     Result |= SymbolRef::SF_Weak;
-    // We use indirect to allow the archiver to write weak externs
-    Result |= SymbolRef::SF_Indirect;
+    if (AWE->Characteristics != COFF::IMAGE_WEAK_EXTERN_SEARCH_ALIAS)
+      Result |= SymbolRef::SF_Undefined;
   }
 
   if (Symb.getSectionNumber() == COFF::IMAGE_SYM_ABSOLUTE)
@@ -235,7 +235,7 @@ uint32_t COFFObjectFile::getSymbolFlags(DataRefImpl Ref) const {
   if (Symb.isCommon())
     Result |= SymbolRef::SF_Common;
 
-  if (Symb.isAnyUndefined())
+  if (Symb.isUndefined())
     Result |= SymbolRef::SF_Undefined;
 
   return Result;

llvm/test/tools/llvm-ar/coff-weak.yaml

@@ -0,0 +1,53 @@
+# RUN: yaml2obj %s -o %t.obj
+#
+# RUN: rm -f %t.ar
+# RUN: llvm-ar crs %t.a %t.obj
+# RUN: llvm-nm -print-armap %t.a | FileCheck %s
+
+# CHECK: Archive map
+# CHECK-NEXT: WeakSearchAlias in coff-weak.yaml.tmp.obj
+# CHECK-EMPTY:
+
+--- !COFF
+header:
+  Machine:         IMAGE_FILE_MACHINE_UNKNOWN
+  Characteristics: [  ]
+sections:
+  - Name:            .drectve
+    Characteristics: [ IMAGE_SCN_LNK_INFO, IMAGE_SCN_LNK_REMOVE ]
+    SectionData:     ''
+symbols:
+  - Name:            NormalUndefined
+    Value:           0
+    SectionNumber:   0
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            WeakSearchAlias
+    Value:           0
+    SectionNumber:   0
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_WEAK_EXTERNAL
+    WeakExternal:
+      TagIndex:        0
+      Characteristics: IMAGE_WEAK_EXTERN_SEARCH_ALIAS
+  - Name:            WeakSearchLibrary
+    Value:           0
+    SectionNumber:   0
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_WEAK_EXTERNAL
+    WeakExternal:
+      TagIndex:        0
+      Characteristics: IMAGE_WEAK_EXTERN_SEARCH_LIBRARY
+  - Name:            WeakSearchNolibrary
+    Value:           0
+    SectionNumber:   0
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_WEAK_EXTERNAL
+    WeakExternal:
+      TagIndex:        0
+      Characteristics: IMAGE_WEAK_EXTERN_SEARCH_NOLIBRARY
+...

llvm/test/tools/llvm-dlltool/coff-decorated.def

@@ -22,5 +22,5 @@ StdcallAlias@4==StdcallFunction@4
 ; CHECK: Name type: name
 ; CHECK: Symbol: __imp_??_7exception@@6B@
 ; CHECK: Symbol: ??_7exception@@6B@
-; CHECK-NM: w _StdcallAlias@4
+; CHECK-NM: W _StdcallAlias@4
 ; CHECK-NM: U _StdcallFunction@4

llvm/test/tools/llvm-dlltool/coff-weak-exports.def

@@ -15,14 +15,14 @@ ImpLibName2 = Implementation2 == AltTestFunction2
 ImpLibName3 = kernel32.Sleep
 
 ; CHECK:      U AltTestFunction
-; CHECK-NEXT: w TestFunction
+; CHECK-NEXT: W TestFunction
 ; CHECK:      U __imp_AltTestFunction
-; CHECK-NEXT: w __imp_TestFunction
+; CHECK-NEXT: W __imp_TestFunction
 ; CHECK:      T ImpLibName
 ; CHECK-NEXT: T __imp_ImpLibName
 ; CHECK:      U AltTestFunction2
-; CHECK-NEXT: w ImpLibName2
+; CHECK-NEXT: W ImpLibName2
 ; CHECK:      U __imp_AltTestFunction2
-; CHECK-NEXT: w __imp_ImpLibName2
+; CHECK-NEXT: W __imp_ImpLibName2
 ; CHECK:      T ImpLibName3
 ; CHECK-NEXT: T __imp_ImpLibName3