Implement GetThreadCount for Linux.

src/gtest-port.cc

@@ -35,6 +35,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <fstream>
 
 #if GTEST_OS_WINDOWS
 # include <windows.h>
@@ -83,10 +84,31 @@ const int kStdOutFileno = STDOUT_FILENO;
 const int kStdErrFileno = STDERR_FILENO;
 #endif  // _MSC_VER
 
-#if GTEST_OS_MAC
+#if GTEST_OS_LINUX
+
+namespace {
+template <typename T>
+T ReadProcFileField(const string& filename, int field) {
+  std::string dummy;
+  std::ifstream file(filename.c_str());
+  while (field-- > 0) {
+    file >> dummy;
+  }
+  T output = 0;
+  file >> output;
+  return output;
+}
+}  // namespace
+
+// Returns the number of active threads, or 0 when there is an error.
+size_t GetThreadCount() {
+  const string filename =
+      (Message() << "/proc/" << getpid() << "/stat").GetString();
+  return ReadProcFileField<int>(filename, 19);
+}
+
+#elif GTEST_OS_MAC
 
-// Returns the number of threads running in the process, or 0 to indicate that
-// we cannot detect it.
 size_t GetThreadCount() {
   const task_t task = mach_task_self();
   mach_msg_type_number_t thread_count;
@@ -132,7 +154,7 @@ size_t GetThreadCount() {
   return 0;
 }
 
-#endif  // GTEST_OS_MAC
+#endif  // GTEST_OS_LINUX
 
 #if GTEST_IS_THREADSAFE && GTEST_OS_WINDOWS