Add ___Z demangling to new common demangle function

[jhenderson]

Summary

This is a follow-up to rL351448. This change adds support for the ___Z extension of Itanium demangling, requested by @erik.pilkington in the previous review, to the newly available demangle function.

[erik.pilkington]

LGTM, thanks for following up!

[erik.pilkington]

lib/Demangle/Demangle.cpp

18–19 ↗

(On Diff #182290)

As of r351481, we allow leading underscores on these. Maybe it would be easier to flip this around so we call microsoftDemangle if the name starts with ?, then itaniumDemangle otherwise?

[grimar]

minor nit:

lib/Demangle/Demangle.cpp

19 ↗

(On Diff #182290)

I wonder if

MangledName.compare(0, string::npos, "___Z")

would be a bit more readable way here?
("A value of string::npos indicates all characters until the end of the string.",
http://www.cplusplus.com/reference/string/string/compare/)

[grimar]

lib/Demangle/Demangle.cpp

19 ↗

(On Diff #182290)

I think there is no much difference. I just had to count the amount of '_`, but the initial version is better I think now.

[grimar]

lib/Demangle/Demangle.cpp

19 ↗

(On Diff #182290)

Oh, and I just misread the spec :) Please ignore this comments.

[jhenderson]

lib/Demangle/Demangle.cpp

18–19 ↗

(On Diff #182290)

@erik.pilkington, flipping it around would adversely affect the behaviour, because itaniumDemangle can also do demangling of types, which aren't strictly fully encoded mangled names. Based on code-inspection, I believe an input string of, say, 'v', would become 'void', which is clearly wrong behaviour for a variable with the name 'v'. At the same time, having to check for _Z, __Z, ___Z and ____Z seems silly. I'll see if I can come up with a better solution.

@grimar, my understanding is that it would compare the entirety of the first string against the other side, which would fail (unless the string was for example "_Z"). Is that what you understand after your re-read?

[grimar]

lib/Demangle/Demangle.cpp

18–19 ↗

(On Diff #182290)

Yes, I mixed "compared string" with "comparing string". Sorry for the noise.

[jhenderson]

Handle __Z and ____Z too.

[grimar]

LGTM.

lib/Demangle/Demangle.cpp

17 ↗

(On Diff #182495)

Using just size_t form seems to be much more common. But I see std::size_t is also used sometimes.
Up to you. FTR in LLD we use size_t.

20 ↗

(On Diff #182495)

Up to you again, but I would use just I or Pos for shortness:

std::size_t I = MangledName.find_first_not_of('_');
return I > 0 && I <= 4 && MangledName[I] == 'Z';

[jhenderson]

lib/Demangle/Demangle.cpp

17 ↗

(On Diff #182495)

Looks like ItaniumDemangle.cpp exclusively uses just size_t, so I'll do that.

20 ↗

(On Diff #182495)

Pos is fine by me.

llvm/trunk/lib/Demangle/Demangle.cpp

 //===-- Demangle.cpp - Common demangling functions ------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file This file contains definitions of common demangling functions.
 ///
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Demangle/Demangle.h"
 
+static bool isItaniumEncoding(const std::string &MangledName) {
+  size_t Pos = MangledName.find_first_not_of('_');
+  // A valid Itanium encoding requires 1-4 leading underscores, followed by 'Z'.
+  return Pos > 0 && Pos <= 4 && MangledName[Pos] == 'Z';
+}
+
 std::string llvm::demangle(const std::string &MangledName) {
   char *Demangled;
-  if (MangledName.compare(0, 2, "_Z") == 0)
+  if (isItaniumEncoding(MangledName))
     Demangled = itaniumDemangle(MangledName.c_str(), nullptr, nullptr, nullptr);
   else
     Demangled =
         microsoftDemangle(MangledName.c_str(), nullptr, nullptr, nullptr);
 
   if (!Demangled)
     return MangledName;
 
   std::string Ret = Demangled;
   free(Demangled);
   return Ret;
 }

llvm/trunk/unittests/Demangle/DemangleTest.cpp

 //===-- DemangleTest.cpp --------------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Demangle/Demangle.h"
 #include "gmock/gmock.h"
 
 using namespace llvm;
 
 TEST(Demangle, demangleTest) {
+  EXPECT_EQ(demangle("_"), "_");
   EXPECT_EQ(demangle("_Z3fooi"), "foo(int)");
+  EXPECT_EQ(demangle("__Z3fooi"), "foo(int)");
+  EXPECT_EQ(demangle("___Z3fooi_block_invoke"),
+            "invocation function for block in foo(int)");
+  EXPECT_EQ(demangle("____Z3fooi_block_invoke"),
+            "invocation function for block in foo(int)");
   EXPECT_EQ(demangle("?foo@@YAXH@Z"), "void __cdecl foo(int)");
   EXPECT_EQ(demangle("foo"), "foo");
 }