[lld] r320792 - [COFF] Warn for locally imported symbols

[Shoaib Meenai via llvm-commits]

Author: smeenai
Date: Thu Dec 14 23:49:21 2017
New Revision: 320792

URL: http://llvm.org/viewvc/llvm-project?rev=320792&view=rev
Log:
[COFF] Warn for locally imported symbols

Locally imported symbols are a very surprising linker feature. link.exe
warns for them, and we should warn too.

Differential Revision: https://reviews.llvm.org/D41269

Added:
    lld/trunk/test/COFF/Inputs/locally-imported-def.s
    lld/trunk/test/COFF/Inputs/locally-imported-imp.s
    lld/trunk/test/COFF/locally-imported-warn-multiple.s
Modified:
    lld/trunk/COFF/SymbolTable.cpp
    lld/trunk/test/COFF/locally-imported.test

Modified: lld/trunk/COFF/SymbolTable.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/SymbolTable.cpp?rev=320792&r1=320791&r2=320792&view=diff
==============================================================================
--- lld/trunk/COFF/SymbolTable.cpp (original)
+++ lld/trunk/COFF/SymbolTable.cpp Thu Dec 14 23:49:21 2017
@@ -63,6 +63,7 @@ static void errorOrWarn(const Twine &S)
 
 void SymbolTable::reportRemainingUndefines() {
   SmallPtrSet<Symbol *, 8> Undefs;
+  DenseMap<Symbol *, Symbol *> LocalImports;
 
   for (auto &I : SymMap) {
     Symbol *Sym = I.second;
@@ -98,6 +99,7 @@ void SymbolTable::reportRemainingUndefin
         auto *D = cast<Defined>(Imp);
         replaceSymbol<DefinedLocalImport>(Sym, Name, D);
         LocalImportChunks.push_back(cast<DefinedLocalImport>(Sym)->getChunk());
+        LocalImports[Sym] = D;
         continue;
       }
     }
@@ -109,17 +111,28 @@ void SymbolTable::reportRemainingUndefin
     Undefs.insert(Sym);
   }
 
-  if (Undefs.empty())
+  if (Undefs.empty() && LocalImports.empty())
     return;
 
-  for (Symbol *B : Config->GCRoot)
+  for (Symbol *B : Config->GCRoot) {
     if (Undefs.count(B))
       errorOrWarn("<root>: undefined symbol: " + B->getName());
+    if (Symbol *Imp = LocalImports.lookup(B))
+      warn("<root>: locally defined symbol imported: " + Imp->getName() +
+           " (defined in " + toString(Imp->getFile()) + ")");
+  }
 
-  for (ObjFile *File : ObjFile::Instances)
-    for (Symbol *Sym : File->getSymbols())
-      if (Sym && Undefs.count(Sym))
+  for (ObjFile *File : ObjFile::Instances) {
+    for (Symbol *Sym : File->getSymbols()) {
+      if (!Sym)
+        continue;
+      if (Undefs.count(Sym))
         errorOrWarn(toString(File) + ": undefined symbol: " + Sym->getName());
+      if (Symbol *Imp = LocalImports.lookup(Sym))
+        warn(toString(File) + ": locally defined symbol imported: " +
+             Imp->getName() + " (defined in " + toString(Imp->getFile()) + ")");
+    }
+  }
 }
 
 std::pair<Symbol *, bool> SymbolTable::insert(StringRef Name) {

Added: lld/trunk/test/COFF/Inputs/locally-imported-def.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/Inputs/locally-imported-def.s?rev=320792&view=auto
==============================================================================
--- lld/trunk/test/COFF/Inputs/locally-imported-def.s (added)
+++ lld/trunk/test/COFF/Inputs/locally-imported-def.s Thu Dec 14 23:49:21 2017
@@ -0,0 +1,4 @@
+.text
+.globl f
+f:
+	ret

Added: lld/trunk/test/COFF/Inputs/locally-imported-imp.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/Inputs/locally-imported-imp.s?rev=320792&view=auto
==============================================================================
--- lld/trunk/test/COFF/Inputs/locally-imported-imp.s (added)
+++ lld/trunk/test/COFF/Inputs/locally-imported-imp.s Thu Dec 14 23:49:21 2017
@@ -0,0 +1,2 @@
+.text
+	call	__imp_f

Added: lld/trunk/test/COFF/locally-imported-warn-multiple.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/locally-imported-warn-multiple.s?rev=320792&view=auto
==============================================================================
--- lld/trunk/test/COFF/locally-imported-warn-multiple.s (added)
+++ lld/trunk/test/COFF/locally-imported-warn-multiple.s Thu Dec 14 23:49:21 2017
@@ -0,0 +1,14 @@
+# REQUIRES: x86
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-windows-msvc -o %T/locally-imported-def.obj %S/Inputs/locally-imported-def.s
+# RUN: llvm-mc -filetype=obj -triple=x86_64-windows-msvc -o %T/locally-imported-imp1.obj %S/Inputs/locally-imported-imp.s
+# RUN: llvm-mc -filetype=obj -triple=x86_64-windows-msvc -o %T/locally-imported-imp2.obj %S/Inputs/locally-imported-imp.s
+# RUN: llvm-mc -filetype=obj -triple=x86_64-windows-msvc -o %t.obj %s
+# RUN: lld-link /entry:main %T/locally-imported-def.obj %T/locally-imported-imp1.obj %T/locally-imported-imp2.obj %t.obj 2>&1 | FileCheck %s
+
+# CHECK: warning: [[TESTDIR:[^:]+]]locally-imported-imp1.obj: locally defined symbol imported: f (defined in [[TESTDIR]]locally-imported-def.obj)
+# CHECK-NEXT: warning: [[TESTDIR:[^:]+]]locally-imported-imp2.obj: locally defined symbol imported: f (defined in [[TESTDIR]]locally-imported-def.obj)
+
+.globl main
+main:
+	ret

Modified: lld/trunk/test/COFF/locally-imported.test
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/locally-imported.test?rev=320792&r1=320791&r2=320792&view=diff
==============================================================================
--- lld/trunk/test/COFF/locally-imported.test (original)
+++ lld/trunk/test/COFF/locally-imported.test Thu Dec 14 23:49:21 2017
@@ -1,8 +1,10 @@
 # RUN: yaml2obj < %s > %t.obj
-# RUN: lld-link /out:%t.exe /entry:main %t.obj
+# RUN: lld-link /out:%t.exe /entry:main %t.obj 2>&1 | FileCheck -check-prefix=WARN %s
 # RUN: llvm-objdump -s %t.exe | FileCheck %s
 # RUN: llvm-readobj -coff-basereloc %t.exe | FileCheck -check-prefix=BASEREL %s
 
+# WARN: warning: [[INPUT:[^:]+]]: locally defined symbol imported: main (defined in [[INPUT]])
+
 # CHECK:      Contents of section .text:
 # CHECK-NEXT: 1000 00200000
 # CHECK:      Contents of section .rdata: