cpp: convert ServerPidFile() and ServerPidSymlink() into constants

These two functions have no logic inside it, they just return a string, and a
string that does not change, so they might be better expressed as real C/C++
constants. This might as well generate some better (and less) code anyway.

--
Change-Id: I78673c537c17c2665a74c5778e45a4d41a5f7b50
Reviewed-on: https://bazel-review.googlesource.com/#/c/6114
MOS_MIGRATED_REVID=133805201

src/main/cpp/blaze.cc

@@ -1000,8 +1000,8 @@ static int GetServerPid(const string &server_dir) {
   // TODO(lberki): Remove the readlink() call when there is no chance of an old
   // server lingering around. Probably safe after 2016.06.01.
   int len;
-  string pid_file = blaze_util::JoinPath(server_dir, ServerPidFile());
-  string pid_symlink = blaze_util::JoinPath(server_dir, ServerPidSymlink());
+  string pid_file = blaze_util::JoinPath(server_dir, kServerPidFile);
+  string pid_symlink = blaze_util::JoinPath(server_dir, kServerPidSymlink);
   len = readlink(pid_symlink.c_str(), buf, sizeof(buf) - 1);
   if (len < 0) {
     int fd = open(pid_file.c_str(), O_RDONLY);

src/main/cpp/blaze_util.cc

@@ -45,13 +45,8 @@ using std::vector;
 
 namespace blaze {
 
-string ServerPidFile() {
-  return "server.pid.txt";
-}
-
-string ServerPidSymlink() {
-  return "server.pid";
-}
+const char kServerPidFile[] = "server.pid.txt";
+const char kServerPidSymlink[] = "server.pid";
 
 string GetUserName() {
   const char *user = getenv("USER");

src/main/cpp/blaze_util.h

@@ -29,9 +29,8 @@ namespace blaze {
 
 using std::string;
 
-string ServerPidFile();
-
-string ServerPidSymlink();
+extern const char kServerPidFile[];
+extern const char kServerPidSymlink[];
 
 string GetUserName();
 

src/main/cpp/blaze_util_mingw.cc

@@ -394,7 +394,7 @@ void ExecuteDaemon(const string& exe, const std::vector<string>& args_vector,
   CloseHandle(pipe_read);
 
   string pid_string = ToString(processInfo.dwProcessId);
-  string pid_file = blaze_util::JoinPath(server_dir, ServerPidFile());
+  string pid_file = blaze_util::JoinPath(server_dir, kServerPidFile);
   if (!WriteFile(pid_string, pid_file)) {
     // Not a lot we can do if this fails
     fprintf(stderr, "Cannot write PID file %s\n", pid_file.c_str());

src/main/cpp/blaze_util_posix.cc

@@ -153,9 +153,8 @@ void ExecuteDaemon(const string& exe,
 
   Daemonize(daemon_output);
   string pid_string = ToString(getpid());
-  string pid_file = blaze_util::JoinPath(server_dir, ServerPidFile());
-  string pid_symlink_file =
-      blaze_util::JoinPath(server_dir, ServerPidSymlink());
+  string pid_file = blaze_util::JoinPath(server_dir, kServerPidFile);
+  string pid_symlink_file = blaze_util::JoinPath(server_dir, kServerPidSymlink);
 
   if (!WriteFile(pid_string, pid_file)) {
     // The exit code does not matter because we are already in the daemonized