[llvm-cxxfilt] Replace isalnum with isAlnum from StringExtras

[tmiasko]

Summary

D104366 introduced a new llvm-cxxfilt test with non-ASCII characters,
which caused a failure on llvm-clang-x86_64-expensive-checks-win
builder, with a stack trace suggesting issue in a call to isalnum.

The argument to isalnum should be either EOF or a value that is
representable in the type unsigned char. The llvm-cxxfilt does not
perform a cast from char to unsigned char before the call, so the
value might be out of valid range.

Replace the call to isalnum with isAlnum from StringExtras, which takes
a char as the argument. This also makes the check independent of the
current locale.

[dblaikie]

Generally if a patch requires review, that's probably too long a turnaround to leave something broken on a buildbot - probably worth reverting the other patch, maybe including this change in that patch - or possibly committing this separately if possible especially if it can be tested independently.

[Orlando]

Hi, the change to llvm/test/tools/llvm-cxxfilt/delimiters.test caused it to fail when run from cmd.exe. I've put up D111072 for review as a work around.

llvm/test/tools/llvm-cxxfilt/delimiters.test

 RUN:      '_Z3Foo\'   \
 RUN:      '_Z3Foo]'   \
 RUN:      '_Z3Foo^'   \
 RUN:      '_Z3Foo`'   \
 RUN:      "\"_Z3Foo{\"" \
 RUN:      '_Z3Foo|'   \
 RUN:      '_Z3Foo}'   \
 RUN:      '_Z3Foo~,,' \
+RUN:      '_Z3Foo⦙_Z3Bar' \
 RUN:      '_Z3Foo,,_Z3Bar::_Z3Baz  _Z3Foo,_Z3Bar:_Z3Baz' \
 RUN:      '_Z3Foo$ ._Z3Foo' | llvm-cxxfilt -n | FileCheck %s
 
 CHECK: ,,Foo!
 CHECK: Foo"
 CHECK: Foo#
 CHECK: Foo%
 CHECK: Foo&

 CHECK: Foo\
 CHECK: Foo]
 CHECK: Foo^
 CHECK: Foo`
 CHECK: Foo{
 CHECK: Foo|
 CHECK: Foo}
 CHECK: Foo~,,
+CHECK: Foo⦙Bar
 CHECK: Foo,,Bar::Baz  Foo,Bar:Baz
 CHECK: _Z3Foo$ ._Z3Foo

llvm/tools/llvm-cxxfilt/llvm-cxxfilt.cpp

static void SplitStringDelims(
   }
 }
 
 // This returns true if 'C' is a character that can show up in an
 // Itanium-mangled string.
 static bool IsLegalItaniumChar(char C) {
   // Itanium CXX ABI [External Names]p5.1.1:
   // '$' and '.' in mangled names are reserved for private implementations.
-  return isalnum(C) || C == '.' || C == '$' || C == '_';
+  return isAlnum(C) || C == '.' || C == '$' || C == '_';
 }
 
 // If 'Split' is true, then 'Mangled' is broken into individual words and each
 // word is demangled.  Otherwise, the entire string is treated as a single
 // mangled item.  The result is output to 'OS'.
 static void demangleLine(llvm::raw_ostream &OS, StringRef Mangled, bool Split) {
   std::string Result;
   if (Split) {