From: Johannes Sixt <j6t@kdbg.org>
To: Johannes Schindelin <johannes.schindelin@gmx.de>
Cc: git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
Pranit Bauva <pranit.bauva@gmail.com>
Subject: Re: [PATCH 1/1] mingw: intercept isatty() to handle /dev/null as Git expects it
Date: Fri, 16 Dec 2016 18:48:01 +0100 [thread overview]
Message-ID: <129f000c-49c1-0e75-26b3-c96e9b442443@kdbg.org> (raw)
In-Reply-To: <42ddc270ea04e01e899cc479063e5d602e4a4448.1481454992.git.johannes.schindelin@gmx.de>
Am 11.12.2016 um 12:16 schrieb Johannes Schindelin:
> When Git's source code calls isatty(), it really asks whether the
> respective file descriptor is connected to an interactive terminal.
>
> Windows' _isatty() function, however, determines whether the file
> descriptor is associated with a character device. And NUL, Windows'
> equivalent of /dev/null, is a character device.
>
> Which means that for years, Git mistakenly detected an associated
> interactive terminal when being run through the test suite, which
> almost always redirects stdin, stdout and stderr to /dev/null.
>
> This bug only became obvious, and painfully so, when the new
> bisect--helper entered the `pu` branch and made the automatic build & test
> time out because t6030 was waiting for an answer.
>
> For details, see
>
> https://msdn.microsoft.com/en-us/library/f4s0ddew.aspx
>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---
> compat/mingw.h | 3 +++
> compat/winansi.c | 33 +++++++++++++++++++++++++++++++++
> 2 files changed, 36 insertions(+)
>
> diff --git a/compat/mingw.h b/compat/mingw.h
> index 034fff9479..3350169555 100644
> --- a/compat/mingw.h
> +++ b/compat/mingw.h
> @@ -384,6 +384,9 @@ int mingw_raise(int sig);
> * ANSI emulation wrappers
> */
>
> +int winansi_isatty(int fd);
> +#define isatty winansi_isatty
> +
> void winansi_init(void);
> HANDLE winansi_get_osfhandle(int fd);
>
> diff --git a/compat/winansi.c b/compat/winansi.c
> index db4a5b0a37..cb725fb02f 100644
> --- a/compat/winansi.c
> +++ b/compat/winansi.c
> @@ -7,6 +7,9 @@
> #include <wingdi.h>
> #include <winreg.h>
>
> +/* In this file, we actually want to use Windows' own isatty(). */
> +#undef isatty
> +
> /*
> ANSI codes used by git: m, K
>
> @@ -570,6 +573,36 @@ static void detect_msys_tty(int fd)
>
> #endif
>
> +int winansi_isatty(int fd)
> +{
> + int res = isatty(fd);
> +
> + if (res) {
> + /*
> + * Make sure that /dev/null is not fooling Git into believing
> + * that we are connected to a terminal, as "_isatty() returns a
> + * nonzero value if the descriptor is associated with a
> + * character device."; for more information, see
> + *
> + * https://msdn.microsoft.com/en-us/library/f4s0ddew.aspx
> + */
> + HANDLE handle = (HANDLE)_get_osfhandle(fd);
> + if (fd == STDIN_FILENO) {
> + DWORD dummy;
> +
> + if (!GetConsoleMode(handle, &dummy))
> + res = 0;
> + } else if (fd == STDOUT_FILENO || fd == STDERR_FILENO) {
> + CONSOLE_SCREEN_BUFFER_INFO dummy;
> +
> + if (!GetConsoleScreenBufferInfo(handle, &dummy))
> + res = 0;
I am sorry to have to report that this check does not work as expected.
I am operating Git from CMD, not mintty, BTW.
It fails with GetLastError() == 6 (invalid handle value). The reason for
this is, I think, that in reality we are not writing to the console
directly, but to a pipe, which is drained by console_thread(), which
writes to the console.
I have little clue what this winansi.c file is doing. Do you have any
pointers where I should start digging?
Wait...
Should we not use winansi_get_osfhandle() instead of _get_osfhandle()?
> + }
> + }
> +
> + return res;
> +}
> +
> void winansi_init(void)
> {
> int con1, con2;
>
next prev parent reply other threads:[~2016-12-16 17:48 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-11 11:16 [PATCH 0/1] Fix a long-standing isatty() problem on Windows Johannes Schindelin
2016-12-11 11:16 ` [PATCH 1/1] mingw: intercept isatty() to handle /dev/null as Git expects it Johannes Schindelin
2016-12-16 17:48 ` Johannes Sixt [this message]
2016-12-16 18:08 ` Junio C Hamano
2016-12-16 18:44 ` Johannes Sixt
2016-12-16 19:05 ` Junio C Hamano
2016-12-21 17:56 ` Johannes Schindelin
2016-12-18 15:26 ` [PATCH] winansi_isatty(): fix when Git is used from CMD Johannes Sixt
2016-12-18 15:37 ` Johannes Sixt
2016-12-19 19:34 ` Johannes Sixt
2016-12-21 17:57 ` Johannes Schindelin
2016-12-20 16:53 ` Johannes Schindelin
2016-12-19 1:12 ` Junio C Hamano
2016-12-20 16:50 ` Johannes Schindelin
2016-12-20 16:59 ` Junio C Hamano
2016-12-21 17:59 ` Johannes Schindelin
2016-12-21 18:54 ` Junio C Hamano
2016-12-22 9:23 ` Johannes Schindelin
2016-12-11 17:49 ` [PATCH 0/1] Fix a long-standing isatty() problem on Windows Junio C Hamano
2016-12-12 9:59 ` Johannes Schindelin
2016-12-12 16:46 ` Junio C Hamano
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