Add a binary to dump demangled names.

Test: Ran the executable and verified names get demangled.
Test: Ran with the -c option to verify it compares demangled names.
Change-Id: I9118ccc4398980346d26f615cdfed0bb756b52fe

demangle/Android.bp

@@ -43,6 +43,15 @@ cc_library {
     ],
 }
 
+cc_binary {
+    name: "demangle",
+    defaults: ["libdemangle_defaults"],
+    srcs: ["demangle.cpp"],
+    host_supported: true,
+
+    shared_libs: ["libdemangle"],
+}
+
 //-------------------------------------------------------------------------
 // Unit Tests
 //-------------------------------------------------------------------------

demangle/demangle.cpp

@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <getopt.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <string>
+
+#include <demangle.h>
+
+extern "C" char* __cxa_demangle(const char*, char*, size_t*, int*);
+
+void usage(const char* prog_name) {
+  printf("Usage: %s [-c] <NAME_TO_DEMANGLE>\n", prog_name);
+  printf("  -c\n");
+  printf("    Compare the results of __cxa_demangle against the current\n");
+  printf("    demangler.\n");
+}
+
+std::string DemangleWithCxa(const char* name) {
+  const char* cxa_demangle = __cxa_demangle(name, nullptr, nullptr, nullptr);
+
+  if (cxa_demangle == nullptr) {
+    return name;
+  }
+
+  // The format of our demangler is slightly different from the cxa demangler
+  // so modify the cxa demangler output. Specifically, for templates, remove
+  // the spaces between '>' and '>'.
+  std::string demangled_str;
+  for (size_t i = 0; i < strlen(cxa_demangle); i++) {
+    if (i > 2 && cxa_demangle[i] == '>' && std::isspace(cxa_demangle[i - 1]) &&
+        cxa_demangle[i - 2] == '>') {
+      demangled_str.resize(demangled_str.size() - 1);
+    }
+    demangled_str += cxa_demangle[i];
+  }
+  return demangled_str;
+}
+
+int main(int argc, char** argv) {
+#ifdef __BIONIC__
+  const char* prog_name = getprogname();
+#else
+  const char* prog_name = argv[0];
+#endif
+
+  bool compare = false;
+  int opt_char;
+  while ((opt_char = getopt(argc, argv, "c")) != -1) {
+    if (opt_char == 'c') {
+      compare = true;
+    } else {
+      usage(prog_name);
+      return 1;
+    }
+  }
+  if (optind >= argc || argc - optind != 1) {
+    printf("Must supply a single argument.\n\n");
+    usage(prog_name);
+    return 1;
+  }
+  const char* name = argv[optind];
+
+  std::string demangled_name = demangle(name);
+
+  printf("%s\n", demangled_name.c_str());
+
+  if (compare) {
+    std::string cxa_demangle_str(DemangleWithCxa(name));
+
+    if (cxa_demangle_str != demangled_name) {
+      printf("Mismatch\n");
+      printf("cxa demangle: %s\n", cxa_demangle_str.c_str());
+      return 1;
+    } else {
+      printf("Match\n");
+    }
+  }
+  return 0;
+}