Merge #23: Tell std::system_error() which function failed

d6dac63 Tell std::system_error() which function failed (Vasil Dimov)

Pull request description:

  This would make the error messages a bit more descriptive.

  For example: `ex.what()` could be
  `Invalid argument` before this patch and
  `socketpair: Invalid argument` after this patch.

Top commit has no ACKs.

Tree-SHA512: 95870919c6a0fe2181658a9949ec85bf929aae15f272ebc1f6aca0ccc8fc8f9cc8b5b4023e7dcc6b47aa60331d2603479f6dfb5ae4ac17258d99e90b32353e79

Author: ryanofsky

src/mp/util.cpp

@@ -99,15 +99,15 @@ int SpawnProcess(int& pid, FdToArgsFn&& fd_to_args)
 {
     int fds[2];
     if (socketpair(AF_UNIX, SOCK_STREAM, 0, fds) != 0) {
-        throw std::system_error(errno, std::system_category());
+        throw std::system_error(errno, std::system_category(), "socketpair");
     }
 
     pid = fork();
     if (pid == -1) {
         throw std::system_error(errno, std::system_category(), "fork");
     }
     if (close(fds[pid ? 0 : 1]) != 0) {
-        throw std::system_error(errno, std::system_category());
+        throw std::system_error(errno, std::system_category(), "close");
     }
     if (!pid) {
         int maxFd = MaxFd();
@@ -138,7 +138,7 @@ int WaitProcess(int pid)
 {
     int status;
     if (::waitpid(pid, &status, 0 /* options */) != pid) {
-        throw std::system_error(errno, std::system_category());
+        throw std::system_error(errno, std::system_category(), "waitpid");
     }
     return status;
 }