From: Johannes Sixt <j6t@kdbg.org>
Date: Fri, 18 Dec 2015 20:57:14 GMT
Subject: Re: [PATCH v2] mingw: emulate write(2) that fails with a EPIPE
Message-ID: <5674732A.3050104@kdbg.org>
In-Reply-To: <ca357ac83a9990d6c88b637b76c6cc7f30d3f7be.1450372051.git.johannes.schindelin@gmx.de>

Am 17.12.2015 um 18:08 schrieb Johannes Schindelin:
> On Windows, when writing to a pipe fails, errno is always
> EINVAL. However, Git expects it to be EPIPE.
>
> According to the documentation, there are two cases in which write()
> triggers EINVAL: the buffer is NULL, or the length is odd but the mode
> is 16-bit Unicode (the broken pipe is not mentioned as possible cause).
> Git never sets the file mode to anything but binary, therefore we know
> that errno should actually be EPIPE if it is EINVAL and the buffer is
> not NULL.
>
> See https://msdn.microsoft.com/en-us/library/1570wh78.aspx for more
> details.
>
> This works around t5571.11 failing with v2.6.4 on Windows.
>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---
>   compat/mingw.c | 17 +++++++++++++++++
>   compat/mingw.h |  3 +++
>   2 files changed, 20 insertions(+)
>
> diff --git a/compat/mingw.c b/compat/mingw.c
> index 90bdb1e..5edea29 100644
> --- a/compat/mingw.c
> +++ b/compat/mingw.c
> @@ -394,6 +394,23 @@ int mingw_fflush(FILE *stream)
>   	return ret;
>   }
>
> +#undef write
> +ssize_t mingw_write(int fd, const void *buf, size_t len)
> +{
> +	ssize_t result = write(fd, buf, len);
> +
> +	if (result < 0 && errno == EINVAL && buf) {
> +		/* check if fd is a pipe */
> +		HANDLE h = (HANDLE) _get_osfhandle(fd);
> +		if (GetFileType(h) == FILE_TYPE_PIPE)
> +			errno = EPIPE;
> +		else
> +			errno = EINVAL;
> +	}
> +
> +	return result;
> +}
> +
>   int mingw_access(const char *filename, int mode)
>   {
>   	wchar_t wfilename[MAX_PATH];

Looks good. I tested the patch, and it fixes the failure exposed by 
t5571.11.

Acked-by: Johannes Sixt <j6t@kdbg.org>

Thanks!

-- Hannes