Save and restore errno in signal handler.

runtime/bin/process_linux.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/process.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <signal.h>
 #include <stdio.h>
@@ skipping 70 matching lines @@
 
 static void SetChildOsErrorMessage(char* os_error_message,
                                    int os_error_message_len) {
   SafeStrNCpy(os_error_message, strerror(errno), os_error_message_len);
 }
 
 
 void ExitHandler(int process_signal, siginfo_t* siginfo, void* tmp) {
   int pid = 0;
   int status = 0;
+  // Save errno so it can be restored at the end.
+  int entry_errno = errno;
   while ((pid = TEMP_FAILURE_RETRY(waitpid(-1, &status, WNOHANG))) > 0) {
     int exit_code = 0;
     int negative = 0;
     if (WIFEXITED(status)) {
       exit_code = WEXITSTATUS(status);
     }
     if (WIFSIGNALED(status)) {
       exit_code = WTERMSIG(status);
       negative = 1;
     }
     ProcessInfo* process = LookupProcess(pid);
     if (process != NULL) {
       int message[3] = { pid, exit_code, negative };
       intptr_t result =
           FDUtils::WriteToBlocking(process->fd(), &message, sizeof(message));
       if (result != sizeof(message) && errno != EPIPE) {
         perror("ExitHandler notification failed");
       }
       TEMP_FAILURE_RETRY(close(process->fd()));
     }
   }
+  errno = entry_errno;
 }
 
 
 static void ReportChildError(int exec_control_fd) {
   // In the case of failure in the child process write the errno and
   // the OS error message to the exec control pipe and exit.
   int child_errno = errno;
   char* os_error_message = strerror(errno);
   ASSERT(sizeof(child_errno) == sizeof(errno));
   int bytes_written =
@@ skipping 233 matching lines @@
   if (result == -1) {
     return false;
   }
   return true;
 }
 
 
 void Process::Exit(intptr_t id) {
   RemoveProcess(id);
 }