Proper handling of Itanium mangled names in LLVMSymbolizer on Windows

[eugene]

Summary

Currently on Windows (_MSC_VER) LLVMSymbolizer tries only Microsoft mangling, it makes it difficult to use for crossplat tools.
This fix just explicitly uses itaniumDemangle instead of __cxa_demangle. LLDB on Windows does the same.

[rnk]

lib/DebugInfo/Symbolize/Symbolize.cpp

477

I think we should use itaniumDemangle everywhere so that we have consistent behavior across platforms. At some point, we may be able to add @ruiu's MS demangler below so that we can demangle MS C++ symbols on Linux.

[eugene]

Always using itaniumDemangle

[rnk]

lgtm

lib/DebugInfo/Symbolize/Symbolize.cpp

 #include "SymbolizableObjectFile.h"
 
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/BinaryFormat/COFF.h"
 #include "llvm/Config/config.h"
 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
 #include "llvm/DebugInfo/PDB/PDB.h"
 #include "llvm/DebugInfo/PDB/PDBContext.h"
+#include "llvm/Demangle/Demangle.h"
 #include "llvm/Object/COFF.h"
 #include "llvm/Object/MachO.h"
 #include "llvm/Object/MachOUniversal.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Compression.h"
 #include "llvm/Support/DataExtractor.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/FileSystem.h"

 // Assume that __cxa_demangle is provided by libcxxabi (except for Windows).
 extern "C" char *__cxa_demangle(const char *mangled_name, char *output_buffer,
                                 size_t *length, int *status);
 #endif
 
 std::string
 LLVMSymbolizer::DemangleName(const std::string &Name,
                              const SymbolizableModule *DbiModuleDescriptor) {
-#if !defined(_MSC_VER)
   // We can spoil names of symbols with C linkage, so use an heuristic
   // approach to check if the name should be demangled.
   if (Name.substr(0, 2) == "_Z") {
     int status = 0;
+#if defined(_MSC_VER)
+    char *DemangledName = itaniumDemangle(Name.c_str(), nullptr, nullptr, &status);
+#else
     char *DemangledName = __cxa_demangle(Name.c_str(), nullptr, nullptr, &status);
+#endif
     if (status != 0)
       return Name;
     std::string Result = DemangledName;
     free(DemangledName);
     return Result;
   }
-#else
+
+#if defined(_MSC_VER)
   if (!Name.empty() && Name.front() == '?') {
     // Only do MSVC C++ demangling on symbols starting with '?'.
     char DemangledName[1024] = {0};
     DWORD result = ::UnDecorateSymbolName(
         Name.c_str(), DemangledName, 1023,
         UNDNAME_NO_ACCESS_SPECIFIERS |       // Strip public, private, protected
             UNDNAME_NO_ALLOCATION_LANGUAGE | // Strip __thiscall, __stdcall, etc
             UNDNAME_NO_THROW_SIGNATURES |    // Strip throw() specifications

tools/llvm-symbolizer/CMakeLists.txt

 # FIXME: As we plan to execute llvm-symbolizer binary from compiler-rt
 # libraries, it has to be compiled for all supported targets (x86_64, i386 etc).
 # This means that we need LLVM libraries to be compiled for these
 # targets as well. Currently, there is no support for such a build strategy.
 
 set(LLVM_LINK_COMPONENTS
   DebugInfoDWARF
   DebugInfoPDB
+  Demangle
   Object
   Support
   Symbolize
   )
 
 add_llvm_tool(llvm-symbolizer
   llvm-symbolizer.cpp
   )
 
 if(LLVM_INSTALL_BINUTILS_SYMLINKS)
   add_llvm_tool_symlink(addr2line llvm-symbolizer)
 endif()