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Revision 05d1ed6148305d299693000856e4971e9f642662 authored by Ben Wijen on 22 August 2016, 12:47:55 UTC, committed by Junio C Hamano on 23 August 2016, 16:09:55 UTC 
mingw: ensure temporary file handles are not inherited by child processes
 
When the index is locked and child processes inherit the handle to
said lock and the parent process wants to remove the lock before the
child process exits, on Windows there is a problem: it won't work
because files cannot be deleted if a process holds a handle on them.
The symptom:

    Rename from 'xxx/.git/index.lock' to 'xxx/.git/index' failed.
    Should I try again? (y/n)

Spawning child processes with bInheritHandles==FALSE would not work
because no file handles would be inherited, not even the hStdXxx
handles in STARTUPINFO (stdin/stdout/stderr).

Opening every file with O_NOINHERIT does not work, either, as e.g.
git-upload-pack expects inherited file handles.

This leaves us with the only way out: creating temp files with the
O_NOINHERIT flag. This flag is Windows-specific, however. For our
purposes, it is equivalent to O_CLOEXEC (which does not exist on
Windows), so let's just open temporary files with the O_CLOEXEC flag and
map that flag to O_NOINHERIT on Windows.

As Eric Wong pointed out, we need to be careful to handle the case where
the Linux headers used to compile Git support O_CLOEXEC but the Linux
kernel used to run Git does not: it returns an EINVAL.

This fixes the test that we just introduced to demonstrate the problem.

Signed-off-by: Ben Wijen <ben@wijen.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent ad65f7e
Raw File
kwset.h 
/* This file has been copied from commit e7ac713d^ in the GNU grep git
 * repository. A few small changes have been made to adapt the code to
 * Git.
 */

/* kwset.h - header declaring the keyword set library.
   Copyright (C) 1989, 1998, 2005 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA
   02110-1301, USA.  */

/* Written August 1989 by Mike Haertel.
   The author may be reached (Email) at the address mike@ai.mit.edu,
   or (US mail) as Mike Haertel c/o Free Software Foundation. */

struct kwsmatch
{
  int index;			/* Index number of matching keyword. */
  size_t offset[1];		/* Offset of each submatch. */
  size_t size[1];		/* Length of each submatch. */
};

struct kwset_t;
typedef struct kwset_t* kwset_t;

/* Return an opaque pointer to a newly allocated keyword set, or NULL
   if enough memory cannot be obtained.  The argument if non-NULL
   specifies a table of character translations to be applied to all
   pattern and search text. */
extern kwset_t kwsalloc(unsigned char const *);

/* Incrementally extend the keyword set to include the given string.
   Return NULL for success, or an error message.  Remember an index
   number for each keyword included in the set. */
extern const char *kwsincr(kwset_t, char const *, size_t);

/* When the keyword set has been completely built, prepare it for
   use.  Return NULL for success, or an error message. */
extern const char *kwsprep(kwset_t);

/* Search through the given buffer for a member of the keyword set.
   Return a pointer to the leftmost longest match found, or NULL if
   no match is found.  If foundlen is non-NULL, store the length of
   the matching substring in the integer it points to.  Similarly,
   if foundindex is non-NULL, store the index of the particular
   keyword found therein. */
extern size_t kwsexec(kwset_t, char const *, size_t, struct kwsmatch *);

/* Deallocate the given keyword set and all its associated storage. */
extern void kwsfree(kwset_t);
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