From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Thu, 17 Dec 2015 09:37:19 GMT
Subject: Re: [PATCH] mingw: emulate write(2) that fails with a EPIPE
Message-ID: <alpine.DEB.2.20.1512171035580.6483@virtualbox>
In-Reply-To: <CAPig+cQzCHtyVs47=ASs5V2BSV7gpVszbdTFydiRhnz3gtD2Qw@mail.gmail.com>

Hi Eric,

On Wed, 16 Dec 2015, Eric Sunshine wrote:

> On Wednesday, December 16, 2015, Johannes Schindelin
> <johannes.schindelin@gmx.de> wrote:
> > diff --git a/compat/mingw.h b/compat/mingw.h
> > @@ -210,6 +210,24 @@ FILE *mingw_freopen (const char *filename, const char *otype, FILE *stream);
> > +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) {
> 
> Here, errno is EINVAL...
> 
> > +               /* check if fd is a pipe */
> > +               HANDLE h = (HANDLE) _get_osfhandle(fd);
> > +               if (GetFileType(h) == FILE_TYPE_PIPE)
> > +                       errno = EPIPE;
> > +               else
> > +                       errno = EINVAL;
> 
> Does any of the code between the outer 'if' and this point clobber
> errno, or are you merely assigning EINVAL for robustness against
> future changes?

Yes, it is proofing the code against future changes. And TBH I did not
even bother to check whether _get_osfhandle() or GetFileType() can modify
the errno value, since I *really* wanted to make sure that errno is either
EPIPE or EINVAL in this execution path.

Ciao,
Dscho