win: port multiprocess_exec_test_child.cc

util/test/multiprocess_exec_test_child.cc

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
 #include <errno.h>
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/types.h>
-#include <unistd.h>
 
 #include <algorithm>
 
+#include "build/build_config.h"
+
+#if defined(OS_POSIX)
+#include <unistd.h>
+#elif defined(OS_WIN)
+#include <windows.h>
+#endif
+
 int main(int argc, char* argv[]) {
+#if defined(OS_POSIX)
   // Make sure that there’s nothing open at any FD higher than 3. All FDs other
   // than stdin, stdout, and stderr should have been closed prior to or at
   // exec().
   int max_fd = std::max(static_cast<int>(sysconf(_SC_OPEN_MAX)), OPEN_MAX);
   max_fd = std::max(max_fd, getdtablesize());
   for (int fd = STDERR_FILENO + 1; fd < max_fd; ++fd) {
     if (close(fd) == 0 || errno != EBADF) {
       abort();
     }
   }
 
   // Read a byte from stdin, expecting it to be a specific value.
   char c;
   ssize_t rv = read(STDIN_FILENO, &c, 1);
   if (rv != 1 || c != 'z') {
     abort();
   }
 
   // Write a byte to stdout.
   c = 'Z';
   rv = write(STDOUT_FILENO, &c, 1);
   if (rv != 1) {
     abort();
   }
 
+#elif defined(OS_WIN)
+
+  // Make sure there's nothing open other than stdin, stdout, and stderr.
+  HANDLE handle_stdin = GetStdHandle(STD_INPUT_HANDLE);
+  HANDLE handle_stdout = GetStdHandle(STD_OUTPUT_HANDLE);
+  HANDLE handle_stderr = GetStdHandle(STD_ERROR_HANDLE);
+  // Handles can theoretically go as high as 2^32-4, but in practice they're

[Mark Mentovai, 2015/01/08 17:20:20]

I thought Windows had an API to do this a little more gracefully than looping
over things and closing them (honestly, it’s kind of a hack on the POSIX side
too). Can’t we get the system to give us all of the handles that are available
in the process, along the lines of
http://nsylvain.blogspot.com/2007/09/how-list-all-open-handles.html?

[Mark Mentovai, 2015/01/08 17:20:20]

Blank line before the comment, to make it easier to spot that it’s a new
conceptual “thing.”

[scottmg, 2015/01/08 18:15:53]

Sure, I actually used that at first based on
https://code.google.com/p/chromium/codesearch#chromium/src/sandbox/win/sandbo...,
but it seemed a bit heavy. Switched as it is a bit cleaner.

+  // never that large, so we check only up to 2^16.
+  for (uintptr_t handle_int = 4; handle_int <= 0xffff; handle_int += 4) {
+    HANDLE handle = reinterpret_cast<HANDLE>(handle_int);
+    if (handle == handle_stdin || handle == handle_stdout ||
+        handle == handle_stderr)
+      continue;

[Mark Mentovai, 2015/01/08 17:20:20]

{} me (the condition takes up more than one line, so the bracing helps make it
easier to follow through all that ragged indentation).

[scottmg, 2015/01/08 18:15:53]

Removed.

+    if (CloseHandle(handle)) {

[Mark Mentovai, 2015/01/08 17:20:20]

Can CloseHandle() fail for a reason other than an invalid handle?

[scottmg, 2015/01/08 18:15:53]

I don't know of any reason, but there are so many types that I don't know for
sure. The other way should be more robust to that.

+      abort();
+    }
+  }
+
+  // Read a byte from stdin, expecting it to be a specific value.
+  char c;
+  DWORD bytes_read;
+  if (!ReadFile(handle_stdin, &c, 1, &bytes_read, nullptr) || bytes_read != 1 ||
+      c != 'z') {
+    abort();
+  }
+
+  // Write a byte to stdout.
+  c = 'Z';
+  DWORD bytes_written;
+  if (!WriteFile(handle_stdout, &c, 1, &bytes_written, nullptr) ||
+      bytes_written != 1) {
+    abort();
+  }
+
+#endif  // OS_POSIX
+
   return 0;
 }