[PATCH 1 of 3] serve: add and use portable spawnvp replacement

[Patrick Mezard]

# HG changeset patch
# User Patrick Mezard <pmezard at gmail.com>
# Date 1239391225 -7200
# Node ID 92ac4240b6e0e3c1b959eb481f0e058e61ee705a
# Parent  3ab391dd5ec5ab1f4af06169bde7a9c850a7f4ce
serve: add and use portable spawnvp replacement

There is no standard python command to really detach a process
under Windows. Instead we use the low level API wrapped by
subprocess module with all necessary options to avoid any kind
of context inheritance.

Fix 1/3 for issue421

diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -580,8 +580,7 @@
             elif runargs[i].startswith('--cwd'):
                 del runargs[i:i+2]
                 break
-        pid = os.spawnvp(os.P_NOWAIT | getattr(os, 'P_DETACH', 0),
-                         runargs[0], runargs)
+        pid = util.spawndetached(runargs)
         os.close(wfd)
         os.read(rfd, 1)
         if parentfn:
diff --git a/mercurial/posix.py b/mercurial/posix.py
--- a/mercurial/posix.py
+++ b/mercurial/posix.py
@@ -245,3 +245,8 @@
         return grp.getgrgid(gid)[0]
     except KeyError:
         return str(gid)
+
+def spawndetached(args):
+    return os.spawnvp(os.P_NOWAIT | getattr(os, 'P_DETACH', 0),
+                      args[0], args)
+
diff --git a/mercurial/windows.py b/mercurial/windows.py
--- a/mercurial/windows.py
+++ b/mercurial/windows.py
@@ -7,7 +7,7 @@
 
 from i18n import _
 import osutil, error
-import errno, msvcrt, os, re, sys, random
+import errno, msvcrt, os, re, sys, random, subprocess
 
 nulldev = 'NUL:'
 umask = 002
@@ -59,6 +59,16 @@
             self.close()
             raise IOError(errno.EPIPE, 'Broken pipe')
 
+    # Standard streams descriptors are set to -1 in child processes
+    # not inheriting their parent handles. And raise IOError instead of
+    # ignoring read/write calls.
+    if not hasattr(sys.stdin, 'fileno') or sys.stdin.fileno() == -1:
+        sys.stdin = open(nulldev, 'r')
+    if not hasattr(sys.stderr, 'fileno') or sys.stderr.fileno() == -1:
+        sys.stderr = open(nulldev, 'w')
+    if not hasattr(sys.stdout, 'fileno') or sys.stdout.fileno() == -1:
+        sys.stdout = open(nulldev, 'w')
+
 sys.stdout = winstdout(sys.stdout)
 
 def _is_win_9x():
@@ -321,6 +331,35 @@
             pass
         os.rename(src, dst)
 
+def spawndetached(args):
+    # No standard library function really spawns a fully detached
+    # process under win32 because they allocate pipes or other objects
+    # to handle standard streams communications. Passing these objects
+    # to the child process requires handle inheritance to be enabled
+    # which makes really detached processes impossible.
+
+    class STARTUPINFO:
+        dwFlags = 0
+        hStdInput = None
+        hStdOutput = None
+        hStdError = None
+        wShowWindow = 0
+        
+    path = args[0]
+    args = subprocess.list2cmdline(args)
+    hp, ht, pid, tid = subprocess.CreateProcess(
+        path, args,
+        # no special security
+        None, None,
+        # Do not inherit handles
+        0,
+        # DETACHED_PROCESS
+        0x00000008,
+        os.environ,
+        os.getcwd(),
+        STARTUPINFO())
+    return pid
+
 try:
     # override functions with win32 versions if possible
     from win32 import *