Re: t1308-config-set.sh fails on current master

[Jeff King <peff@peff.net>]

On Wed, Jun 14, 2017 at 01:02:15AM -0400, Jeff King wrote:

> On Wed, Jun 14, 2017 at 04:17:40AM +0200, Øyvind A. Holm wrote:
> 
> > > Interesting.  I'm not able to reproduce it, but of course that doesn't
> > > mean much.
> > 
> > I'll admit that I have a somewhat special build system, but it's been 
> > working great since I created it 7 months ago, and I run the test suite 
> > every time I install a new git. I'm using the Makefile located at
> > 
> >   https://gitlab.com/sunny256/src-other/blob/master/devel/git/Makefile
> > 
> > It's only doing regular stuff like "make configure", "./configure", etc, 
> > but I'm mentioning it in case the Makefile reveals something 
> > interesting. The git installation is in a non-standard location, the 
> > newest version of git I've installed is for example located under 
> > /usr/src-other/pool/git.master.v2.13.1-394-g41dd4330a121/ .
> 
> I couldn't reproduce either with my usual build, but I don't usually use
> autoconf. Running:
> 
>   make configure
>   ./configure
>   make
>   (cd t && ./t1308-*)
> 
> does fail for me. The problem is that the generated config.mak.autogen
> sets the wrong value for FREAD_READS_DIRECTORIES (and overrides the
> default entry for Linux from config.mak.uname. So the configure script
> needs to be fixed.

Actually, I'm not sure if configure.ac is wrong, or the new uses of
FREAD_READS_DIRECTORIES. Because the test configure.ac actually checks:

  FILE *f = fopen(".", "r");
  return f && fread(&c, 1, 1, f);

I.e., it sees that not only do we fopen() a directory, but we actually
read garbage from it. Whereas on Linux, we fopen the file and then the
read gets EISDIR.

So it's not true that FREAD_READS_DIRECTORIES; this is more like
FOPEN_OPENS_DIRECTORIES.

Just looking at how the macro is used, I think we want to handle both
cases the same (by doing an fstat check after fopen). So I think it
would be OK to continue to use FREAD_READS_DIRECTORIES for both cases,
and just fix the configure script. It may be worth updating the macro
name for clarity, though.

-Peff