Merge pull request #8650 from diffblue/run-with-pipe

`run(..., std::ostream &, ...)` with pipe

Author: tautschnig

src/ansi-c/c_preprocess.cpp

@@ -305,8 +305,6 @@ bool c_preprocess_visual_studio(
     command_file << shell_quote(file) << "\n";
   }
 
-  // _popen isn't very reliable on WIN32
-  // that's why we use run()
   int result =
     run("cl", {"cl", "@" + command_file_name()}, "", outstream, stderr_file());
 

src/util/run.cpp

@@ -541,40 +541,119 @@ int run(
 
   return result;
   #else
-  std::string command;
+  int pipefd[2];
+  if(pipe(pipefd) == -1)
+    return -1;
+
+  int stdin_fd = stdio_redirection(STDIN_FILENO, std_input);
+  int stdout_fd = pipefd[1];
+  int stderr_fd = stdio_redirection(STDERR_FILENO, std_error);
 
-  bool first = true;
+  if(stdin_fd == -1 || stdout_fd == -1 || stderr_fd == -1)
+    return 1;
+
+  // temporarily suspend all signals
+  sigset_t new_mask, old_mask;
+  sigemptyset(&new_mask);
+  sigprocmask(SIG_SETMASK, &new_mask, &old_mask);
 
-  // note we use 'what' instead of 'argv[0]' as the name of the executable
-  for(const auto &arg : argv)
+  /* now create new process */
+  pid_t childpid = fork();
+
+  if(childpid >= 0) /* fork succeeded */
   {
-    if(first) // this is argv[0]
+    if(childpid == 0) /* fork() returns 0 to the child process */
     {
-      command += shell_quote(what);
-      first = false;
+      // resume signals
+      remove_signal_catcher();
+      sigprocmask(SIG_SETMASK, &old_mask, nullptr);
+
+      close(pipefd[0]); // unused in child
+
+      std::vector<char *> _argv(argv.size() + 1);
+      for(std::size_t i = 0; i < argv.size(); i++)
+        _argv[i] = strdup(argv[i].c_str());
+
+      _argv[argv.size()] = nullptr;
+
+      if(stdin_fd != STDIN_FILENO)
+        dup2(stdin_fd, STDIN_FILENO);
+      if(stdout_fd != STDOUT_FILENO)
+        dup2(stdout_fd, STDOUT_FILENO);
+      if(stderr_fd != STDERR_FILENO)
+        dup2(stderr_fd, STDERR_FILENO);
+
+      errno = 0;
+      execvp(what.c_str(), _argv.data());
+
+      /* usually no return */
+      perror(std::string("execvp " + what + " failed").c_str());
+      exit(1);
     }
-    else
-      command += " " + shell_quote(arg);
-  }
+    else /* fork() returns new pid to the parent process */
+    {
+      // must do before resuming signals to avoid race
+      register_child(childpid);
 
-  if(!std_input.empty())
-    command += " < " + shell_quote(std_input);
+      // resume signals
+      sigprocmask(SIG_SETMASK, &old_mask, nullptr);
 
-  if(!std_error.empty())
-    command += " 2> " + shell_quote(std_error);
+      close(pipefd[1]); // unused in the parent
+
+      const int buffer_size = 1024;
+      std::vector<char> buffer(buffer_size);
+      ssize_t bytes_read;
 
-  FILE *stream=popen(command.c_str(), "r");
+      while((bytes_read = read(pipefd[0], buffer.data(), buffer_size)) > 0)
+        std_output.write(buffer.data(), bytes_read);
 
-  if(stream!=nullptr)
+      int status; /* parent process: child's exit status */
+
+      /* wait for child to exit, and store its status */
+      while(waitpid(childpid, &status, 0) == -1)
+      {
+        if(errno == EINTR)
+          continue; // try again
+        else
+        {
+          unregister_child();
+
+          perror("Waiting for child process failed");
+          if(stdin_fd != STDIN_FILENO)
+            close(stdin_fd);
+          if(stdout_fd != STDOUT_FILENO)
+            close(stdout_fd);
+          if(stderr_fd != STDERR_FILENO)
+            close(stderr_fd);
+          return 1;
+        }
+      }
+
+      unregister_child();
+
+      if(stdin_fd != STDIN_FILENO)
+        close(stdin_fd);
+      if(stdout_fd != STDOUT_FILENO)
+        close(stdout_fd);
+      if(stderr_fd != STDERR_FILENO)
+        close(stderr_fd);
+
+      return WEXITSTATUS(status);
+    }
+  }
+  else /* fork returns -1 on failure */
   {
-    int ch;
-    while((ch=fgetc(stream))!=EOF)
-      std_output << (unsigned char)ch;
+    // resume signals
+    sigprocmask(SIG_SETMASK, &old_mask, nullptr);
 
-    int result = pclose(stream);
-    return WEXITSTATUS(result);
+    if(stdin_fd != STDIN_FILENO)
+      close(stdin_fd);
+    if(stdout_fd != STDOUT_FILENO)
+      close(stdout_fd);
+    if(stderr_fd != STDERR_FILENO)
+      close(stderr_fd);
+
+    return 1;
   }
-  else
-    return -1;
-  #endif
+#endif
 }