bionic benchmarks: export benchmark library

Export libbenchmark for external projects to write benchmarks against.

Change-Id: I3b04a56a62ce517afc0d5e06dc8d28879ada3d30
diff --git a/benchmarks/benchmark_main.cpp b/benchmarks/benchmark_main.cpp
index 815d56b..7140ab6 100644
--- a/benchmarks/benchmark_main.cpp
+++ b/benchmarks/benchmark_main.cpp
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include "benchmark.h"
+#include <benchmark.h>
 
 #include <regex.h>
 #include <stdio.h>
@@ -29,11 +29,15 @@
 static int64_t g_bytes_processed;
 static int64_t g_benchmark_total_time_ns;
 static int64_t g_benchmark_start_time_ns;
+static int g_name_column_width = 20;
 
 typedef std::map<std::string, ::testing::Benchmark*> BenchmarkMap;
 typedef BenchmarkMap::iterator BenchmarkMapIt;
-static BenchmarkMap g_benchmarks;
-static int g_name_column_width = 20;
+
+static BenchmarkMap& Benchmarks() {
+  static BenchmarkMap benchmarks;
+  return benchmarks;
+}
 
 static int Round(int n) {
   int base = 1;
@@ -98,7 +102,7 @@
     exit(EXIT_FAILURE);
   }
 
-  g_benchmarks.insert(std::make_pair(name, this));
+  Benchmarks().insert(std::make_pair(name, this));
 }
 
 void Benchmark::Run() {
@@ -191,18 +195,18 @@
 }
 
 int main(int argc, char* argv[]) {
-  if (g_benchmarks.empty()) {
+  if (Benchmarks().empty()) {
     fprintf(stderr, "No benchmarks registered!\n");
     exit(EXIT_FAILURE);
   }
 
-  for (BenchmarkMapIt it = g_benchmarks.begin(); it != g_benchmarks.end(); ++it) {
+  for (BenchmarkMapIt it = Benchmarks().begin(); it != Benchmarks().end(); ++it) {
     int name_width = static_cast<int>(strlen(it->second->Name()));
     g_name_column_width = std::max(g_name_column_width, name_width);
   }
 
   bool need_header = true;
-  for (BenchmarkMapIt it = g_benchmarks.begin(); it != g_benchmarks.end(); ++it) {
+  for (BenchmarkMapIt it = Benchmarks().begin(); it != Benchmarks().end(); ++it) {
     ::testing::Benchmark* b = it->second;
     if (b->ShouldRun(argc, argv)) {
       if (need_header) {
@@ -217,7 +221,7 @@
   if (need_header) {
     fprintf(stderr, "No matching benchmarks!\n");
     fprintf(stderr, "Available benchmarks:\n");
-    for (BenchmarkMapIt it = g_benchmarks.begin(); it != g_benchmarks.end(); ++it) {
+    for (BenchmarkMapIt it = Benchmarks().begin(); it != Benchmarks().end(); ++it) {
       fprintf(stderr, "  %s\n", it->second->Name());
     }
     exit(EXIT_FAILURE);