Re: fatal: Could not get current working directory: Permission denied | affected 2.10,2.11,2.12, but not 1.9.5 |

[Jeff King <peff@peff.net>]

On Fri, Mar 17, 2017 at 10:07:18PM +0100, René Scharfe wrote:

> >   As  an extension to the POSIX.1-2001 standard, Linux (libc4, libc5,
> > glibc) getcwd()
> >   allocates the buffer dynamically using malloc(3) if buf is NULL.  In
> > this case, the
> >   allocated buffer has the length size unless size is zero, when buf
> > is allocated as big
> >   as necessary.  The caller should free(3) the returned buffer.
> > 
> > This sounds specific to Linux (though I am reading Linux man pages,
> > which claim this; Also it seems I might have misread it as it also states
> > "The pathname is returned as the function result and via the
> > argument buf, if present.").
> 
> I'm only interested in FreeBSD for now, as that's the platform Zenobiusz
> reported the issue on and I haven't been able to reproduce it, so this is
> still a bit exploratory, but hopefully getting closer.  This extension is
> used in the first version of pwd(1) in FreeBSD's repo, comitted 1994-05-26,
> so it was supported there basically forever.
> 
> The oldest version I found that's using the extention is NetBSD's pwd(1),
> which was committed 1993-03-21 and carries a SCCS timestamp of 1991-02-20.
> Visual Studio .NET 2003 supports it as well.

My big question is what happens on other platforms when they see a NULL
(but 0-sized) buffer. Any reasonable implementation would just return
ERANGE and we'd fall back to the existing code. But we often have to deal with unreasonable ones.

So do we need a "my OS understands getcwd(NULL)" build knob?

-Peff