[PATCH] D52145: lld-link: Also demangle undefined dllimported symbols.

[Nico Weber via Phabricator via llvm-commits]

thakis created this revision.
thakis added a reviewer: ruiu.
Herald added a subscriber: erik.pilkington.

dllimported symbols go through an import stub that's called __imp_ followed by the name the stub points to. Make that work.

Follow-up to https://reviews.llvm.org/D52104


https://reviews.llvm.org/D52145

Files:
  Common/Strings.cpp
  test/COFF/undefined-symbol.s


Index: test/COFF/undefined-symbol.s
===================================================================
--- test/COFF/undefined-symbol.s
+++ test/COFF/undefined-symbol.s
@@ -10,7 +10,7 @@
 # CHECK-NEXT: >>> referenced by {{.*}}.obj:(main)
 # CHECK-NEXT: >>> referenced by {{.*}}.obj:(f1)
 # CHECK-EMPTY:
-# CHECK-NEXT: error: undefined symbol: "int __cdecl baz(void)" (?baz@@YAHXZ)
+# CHECK-NEXT: error: undefined symbol: "__declspec(dllimport) int __cdecl baz(void)" (__imp_?baz@@YAHXZ)
 # CHECK-NEXT: >>> referenced by {{.*}}.obj:(f2)
 
         .section        .text,"xr",one_only,main
@@ -27,4 +27,4 @@
         .section        .text,"xr",one_only,f2
 .globl f2
 f2:
-	call	"?baz@@YAHXZ"
+	callq	*"__imp_?baz@@YAHXZ"(%rip)
Index: Common/Strings.cpp
===================================================================
--- Common/Strings.cpp
+++ Common/Strings.cpp
@@ -38,14 +38,22 @@
 }
 
 Optional<std::string> lld::demangleMSVC(StringRef Name) {
+  // Note: This only works while the check for ? below is present, else a
+  // regular C function that happens to be called __imp__f would be considered
+  // an import stub.
+  std::string prefix;
+  if (Name.consume_front("__imp_"))
+    prefix = "__declspec(dllimport) ";
+
   if (!Name.startswith("?"))
     return None;
+
   char *Buf = microsoftDemangle(Name.str().c_str(), nullptr, nullptr, nullptr);
   if (!Buf)
     return None;
   std::string S(Buf);
   free(Buf);
-  return S;
+  return prefix + S;
 }
 
 StringMatcher::StringMatcher(ArrayRef<StringRef> Pat) {


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