From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.1 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI shortcircuit=no autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 146481F404 for ; Mon, 10 Sep 2018 19:45:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728855AbeIKAks (ORCPT ); Mon, 10 Sep 2018 20:40:48 -0400 Received: from bsmtp7.bon.at ([213.33.87.19]:49665 "EHLO bsmtp7.bon.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728110AbeIKAkr (ORCPT ); Mon, 10 Sep 2018 20:40:47 -0400 Received: from dx.site (unknown [93.83.142.38]) by bsmtp7.bon.at (Postfix) with ESMTPSA id 428JRP67myz5tlR; Mon, 10 Sep 2018 21:45:05 +0200 (CEST) Received: from [IPv6:::1] (localhost [IPv6:::1]) by dx.site (Postfix) with ESMTP id 8B66E2E3D; Mon, 10 Sep 2018 21:45:05 +0200 (CEST) From: Johannes Sixt Subject: Re: [PATCH v2 2/2] mingw: fix mingw_open_append to work with named pipes To: jeffhost@microsoft.com Cc: Jeff Hostetler via GitGitGadget , git@vger.kernel.org, Junio C Hamano References: X-Mozilla-News-Host: news://nntp.gmane.org Message-ID: Date: Mon, 10 Sep 2018 21:45:05 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Am 10.09.18 um 19:05 schrieb Jeff Hostetler via GitGitGadget: > diff --git a/compat/mingw.c b/compat/mingw.c > index 858ca14a57..f87376b26a 100644 > --- a/compat/mingw.c > +++ b/compat/mingw.c > @@ -341,6 +341,19 @@ int mingw_mkdir(const char *path, int mode) > return ret; > } > > +/* > + * Calling CreateFile() using FILE_APPEND_DATA and without FILE_WRITE_DATA > + * is documented in [1] as opening a writable file handle in append mode. > + * (It is believed that) this is atomic since it is maintained by the > + * kernel unlike the O_APPEND flag which is racily maintained by the CRT. > + * > + * [1] https://docs.microsoft.com/en-us/windows/desktop/fileio/file-access-rights-constants > + * > + * This trick does not appear to work for named pipes. Instead it creates > + * a named pipe client handle that cannot be written to. Callers should > + * just use the regular _wopen() for them. (And since client handle gets > + * bound to a unique server handle, it isn't really an issue.) > + */ > static int mingw_open_append(wchar_t const *wfilename, int oflags, ...) > { > HANDLE handle; > @@ -360,10 +373,12 @@ static int mingw_open_append(wchar_t const *wfilename, int oflags, ...) > NULL, create, FILE_ATTRIBUTE_NORMAL, NULL); > if (handle == INVALID_HANDLE_VALUE) > return errno = err_win_to_posix(GetLastError()), -1; > + > /* > * No O_APPEND here, because the CRT uses it only to reset the > - * file pointer to EOF on write(); but that is not necessary > - * for a file created with FILE_APPEND_DATA. > + * file pointer to EOF before each write(); but that is not > + * necessary (and may lead to races) for a file created with > + * FILE_APPEND_DATA. > */ > fd = _open_osfhandle((intptr_t)handle, O_BINARY); > if (fd < 0) > @@ -371,6 +386,23 @@ static int mingw_open_append(wchar_t const *wfilename, int oflags, ...) > return fd; > } > > +#define IS_SBS(ch) (((ch) == '/') || ((ch) == '\\')) > +/* > + * Does the pathname map to the local named pipe filesystem? > + * That is, does it have a "//./pipe/" prefix? > + */ > +static int mingw_is_local_named_pipe_path(const char *filename) > +{ > + return (IS_SBS(filename[0]) && > + IS_SBS(filename[1]) && > + filename[2] == '.' && > + IS_SBS(filename[3]) && > + !strncasecmp(filename+4, "pipe", 4) && > + IS_SBS(filename[8]) && > + filename[9]); > +} > +#undef IS_SBS > + > int mingw_open (const char *filename, int oflags, ...) > { > typedef int (*open_fn_t)(wchar_t const *wfilename, int oflags, ...); > @@ -387,7 +419,7 @@ int mingw_open (const char *filename, int oflags, ...) > if (filename && !strcmp(filename, "/dev/null")) > filename = "nul"; > > - if (oflags & O_APPEND) > + if ((oflags & O_APPEND) && !mingw_is_local_named_pipe_path(filename)) > open_fn = mingw_open_append; > else > open_fn = _wopen; This looks reasonable. I wonder which part of the code uses local named pipes. Is it downstream in Git for Windows or one of the topics in flight? -- Hannes