Re: [PATCH] http: cast result to FILE *

From: Duy Nguyen <pclouds@gmail.com>
Date: Feb 4, 2019, 12:13 UTC
Message-ID: <CACsJy8BtaxMRTG4-r3iJfUuR9k-=r=4QTRxCkFt3k3p7826Z9A@mail.gmail.com>
In-Reply-To: <nycvar.QRO.7.76.6.1902041243220.41@tvgsbejvaqbjf.bet>

On Mon, Feb 4, 2019 at 6:44 PM Johannes Schindelin <Johannes.Schindelin@gmx.de> wrote:

Show 24 quoted lines

>
> Hi Duy,
>
> On Sat, 2 Feb 2019, Duy Nguyen wrote:
>
> > On Sat, Feb 2, 2019 at 4:21 AM Junio C Hamano <gitster@pobox.com> wrote:
> > >
> > > Dan McGregor <dan.mcgregor@usask.ca> writes:
> > >
> > > > Commit 8dd2e88a92 ("http: support file handles for HTTP_KEEP_ERROR",
> > > > 2019-01-10) introduced an implicit assumption that rewind, fileno, and
> > > > fflush are functions. At least on FreeBSD fileno is not, and as such
> > > > passing a void * failed.
> > >
> > > I am not strongly opposed to this patch,
> >
> > Even if this is needed, should it be done behind git-compat-util.h
> > instead? That way if fileno(void*) is used elsewhere, we don't have to
> > do the casting again.
>
> The disadvantage, of course, would be that other call sites would not
> benefit from a manual auditing whether the argument has side effects (and
> thus, whether a macro using the argument multiple times would result in
> very unexpected multiple side effects).

That's just a better reason to "fix" it in compat/. If you define a git_fileno() function and map fileno to it, then you won't have to deal with side effects of FreeBSD's fileno() macro. All evaluation happens before git_fileno() is called.

Show 48 quoted lines

> I'd rather not paper over this issue and thereby open even larger
> problems.
>
> Ciao,
> Dscho
>
> >
> > > but shouldn't you be filing
> > > a bug report against FreeBSD instead?  The implementation is free to
> > > define fileno(fh) as a macro, but it shouldn't force such a change
> > > to conformant programs.
> > >
> > > https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=206146
> > >
> > > > Explicitly cast result to a FILE * when using standard functions that
> > > > may ultimately be macros.
> > > >
> > > > Signed-off-by: Dan McGregor <dan.mcgregor@usask.ca>
> > > > ---
> > > >  http.c | 6 +++---
> > > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/http.c b/http.c
> > > > index 954bebf684..8b9476b151 100644
> > > > --- a/http.c
> > > > +++ b/http.c
> > > > @@ -1996,12 +1996,12 @@ static int http_request_reauth(const char *url,
> > > >               strbuf_reset(result);
> > > >               break;
> > > >       case HTTP_REQUEST_FILE:
> > > > -             if (fflush(result)) {
> > > > +             if (fflush((FILE *)result)) {
> > > >                       error_errno("unable to flush a file");
> > > >                       return HTTP_START_FAILED;
> > > >               }
> > > > -             rewind(result);
> > > > -             if (ftruncate(fileno(result), 0) < 0) {
> > > > +             rewind((FILE *)result);
> > > > +             if (ftruncate(fileno((FILE *)result), 0) < 0) {
> > > >                       error_errno("unable to truncate a file");
> > > >                       return HTTP_START_FAILED;
> > > >               }
> >
> >
> >
> > --
> > Duy
> >

-- 
Duy