From: Junio C Hamano <gitster@pobox.com>
Date: Wed, 16 Dec 2015 18:35:32 GMT
Subject: Re: [PATCH] mingw: emulate write(2) that fails with a EPIPE
Message-ID: <xmqq7fkedyx7.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <01da36219c18373f8507e19035e141d7e56b2d18.1450267413.git.johannes.schindelin@gmx.de>

Johannes Schindelin <johannes.schindelin@gmx.de> writes:

> 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.

Makes sense.

>  int mingw_fflush(FILE *stream);
>  #define fflush mingw_fflush
>  
> +static inline 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;
> +}
> +
> +#define write mingw_write
> +

It strikes me a bit strange to see this inlined compared to what
appears in the context.  Shouldn't the implementation be done in
compat/mingw.c like all others?

>  int mingw_access(const char *filename, int mode);
>  #undef access
>  #define access mingw_access