[LLD] Convert demangleItanium to use the higher level llvm::demangle function. NFC.

[mstorsjo]

Summary

This avoids a few lines of boilerplate of dealing with C string allocations.

Add a testcase for a case where demangling shouldn't happen.

[MaskRay]

This is easier to review than the original patch. Thanks!

[MaskRay]

lld/test/ELF/undef.s

26

add a comment that this is not demangled

lld/Common/Strings.cpp

 
 using namespace llvm;
 using namespace lld;
 
 // Returns the demangled C++ symbol name for Name.
 Optional<std::string> lld::demangleItanium(StringRef name) {
   // itaniumDemangle can be used to demangle strings other than symbol
   // names which do not necessarily start with "_Z". Name can be
-  // either a C or C++ symbol. Don't call itaniumDemangle if the name
+  // either a C or C++ symbol. Don't call demangle if the name
   // does not look like a C++ symbol name to avoid getting unexpected
   // result for a C symbol that happens to match a mangled type name.
   if (!name.startswith("_Z"))
     return None;
 
-  char *buf = itaniumDemangle(name.str().c_str(), nullptr, nullptr, nullptr);
-  if (!buf)
+  std::string demangled = demangle(name);
+  if (demangled == name)
     return None;
-  std::string s(buf);
-  free(buf);
-  return s;
+  return demangled;
 }
 
 StringMatcher::StringMatcher(ArrayRef<StringRef> pat) {
   for (StringRef s : pat) {
     Expected<GlobPattern> pat = GlobPattern::create(s);
     if (!pat)
       error(toString(pat.takeError()));
     else

lld/test/ELF/undef.s

 
 # CHECK: error: undefined symbol: foo(int)
 # CHECK: >>> referenced by undef.s
 # CHECK: >>>               {{.*}}:(.text+0x10)
 
 # CHECK: error: undefined symbol: vtable for Foo
 # CHECK: the vtable symbol may be undefined because the class is missing its key function (see https://lld.llvm.org/missingkeyfunction)
 
+# CHECK: error: undefined symbol: __Z3fooi
+# CHECK: >>> referenced by undef.s
+# CHECK: >>>               {{.*}}:(.text+0x1A)
+
 # CHECK: error: undefined symbol: zed2
 # CHECK: >>> referenced by {{.*}}.o:(.text+0x0) in archive {{.*}}2.a
 
 # CHECK: error: undefined symbol: zed3
 # CHECK: >>> referenced by undef-debug.s:3 (dir{{/|\\}}undef-debug.s:3)
 # CHECK: >>>               {{.*}}.o:(.text+0x0)
 
 # CHECK: error: undefined symbol: zed4
.file "undef.s"
 
   .globl _start
 _start:
   call foo
   call bar
   call zed1
   call _Z3fooi
   call _ZTV3Foo
+  call __Z3fooi