clang_Cursor_getMangling shouldn't mangle if the declaration isn't mangled

[michaelwu]

Summary

Right now clang_Cursor_getMangling will attempt to mangle any declaration, even if the declaration isn't mangled (extern "C"). This results in a partially mangled name which isn't useful for much. This patch makes clang_Cursor_getMangling return an empty string if the declaration isn't mangled.

[rsmith]

tools/libclang/CIndex.cpp

3892

You should use shouldMangleDeclName here instead; this will do the wrong thing if there's an asm label on the declaration (where presumably we do want to list a "mangling").

3893

In this case, we should presumably use the decl's identifier as the "mangled name" rather than just giving up; there could still be backend mangling that applies here, and we should be producing the final symbol name here. In fact, MangleContext::mangleName should probably be changed to produce the identifier name in this case, rather than handling it here.

[michaelwu]

Thanks for the review. I switched to shouldMangleDeclName instead of shouldMangleCXXName, and made it skip the frontend mangling instead of returning an empty string. I tried making mangleName do that instead, but it seemed to cause a bunch of test failures..

The nice thing about returning a valid symbol name instead of an empty string is that I discovered my new test was incomplete. This diff also adds a change to properly handle declarations inside an extern "C".

[michaelwu]

This uses clang_isInvalid in PrintMangledName instead of checking for CXCursor_UnexposedDecl.

[• ehsan]

Landed in r249437.

[michaelwu]

Turns out clang_isUnexposed is what I wanted, rather than clang_isInvalid. I remember seeing clang_isInvalid work though..

test/Index/print-mangled-name.cpp

 // ITANIUM: StructDecl{{.*}}mangled=]
 // MACHO: StructDecl{{.*}}mangled=]
 // MICROSOFT: StructDecl{{.*}}mangled=]
 
 int foo(S, S&);
 // ITANIUM: mangled=_Z3foo1SRS_
 // MACHO: mangled=__Z3foo1SRS_
 // MICROSOFT: mangled=?foo@@YAHUS
+
+extern "C" int foo(int);
+// ITANIUM: mangled=foo
+// MACHO: mangled=_foo
+// MICROSOFT: mangled=_foo

tools/c-index-test/c-index-test.c

 }
 
 /******************************************************************************/
 /* Mangling testing.                                                          */
 /******************************************************************************/
 
 static enum CXChildVisitResult PrintMangledName(CXCursor cursor, CXCursor p,
                                                 CXClientData d) {
+  if (clang_isUnexposed(clang_getCursorKind(cursor)))
+    return CXChildVisit_Recurse;
   CXString MangledName;
   PrintCursor(cursor, NULL);
   MangledName = clang_Cursor_getMangling(cursor);
   printf(" [mangled=%s]\n", clang_getCString(MangledName));
   clang_disposeString(MangledName);
   return CXChildVisit_Continue;
 }
 

tools/libclang/CIndex.cpp

if (!D || !(isa<FunctionDecl>(D) || isa<VarDecl>(D)))
     return cxstring::createEmpty();
 
   // First apply frontend mangling.
   const NamedDecl *ND = cast<NamedDecl>(D);
   ASTContext &Ctx = ND->getASTContext();
   std::unique_ptr<MangleContext> MC(Ctx.createMangleContext());
 
   std::string FrontendBuf;
   llvm::raw_string_ostream FrontendBufOS(FrontendBuf);
+  if (MC->shouldMangleDeclName(ND)) {
     MC->mangleName(ND, FrontendBufOS);
+  } else {
+    ND->printName(FrontendBufOS);
+  }
 
   // Now apply backend mangling.
   std::unique_ptr<llvm::DataLayout> DL(
       new llvm::DataLayout(Ctx.getTargetInfo().getDataLayoutString()));
 
   std::string FinalBuf;
   llvm::raw_string_ostream FinalBufOS(FinalBuf);
   llvm::Mangler::getNameWithPrefix(FinalBufOS, llvm::Twine(FrontendBufOS.str()),