[GiNaC-devel] commit 47a0c68f3e0c4

[Alexei Sheplyakov]

Hi, Jens,

On Tue, May 24, 2011 at 01:15:51AM +0200, Jens Vollinga wrote:

> >tar xaf ginac-1.6.0.tar.bz2
> >mkdir build
> >cd build
> >../ginac-1.6.0/configure --disable-static
> >
> >
> >This fact makes me think that the check is bogus. Also,
> 
> now, at my box there is no warning. I followed the same steps,
> unpacking the tar, doing a vpath build, etc. But no, no warning.
 
> If there were a warning, I would agree that the code in configure.ac
> needs to be fixed.  I would still think it is useful to have a
> summary of possible problems at the end, so my approach would be to
> fix the configure.ac code if necessary, not remove it. But I don't
> get any bogus warning! Does your setup differ significantly from
> mine (Ubuntu 11.04, x64)?

Mine is a minimal Debian (sid) chroot on x86_64. It looks like installing
flex and bison suppress the warning. I think there should be no warning
even if flex and bison are not installed.

> I overlooked the line in the autoconf manual:
> 
> "Be aware that, like most Autoconf macros, they test a feature of
> the host machine, and therefore, they die when cross-compiling."
> 
> But it just confuses me: most Autoconf macros fail when cross-compiling?

For instance, /proc/self/exe might exist on the build system (say, Linux),
and it might be absent on the target system (anything non-Linux). Actually
it might be absent even on Linux if the program runs in a chroot environment.
That's why autoconf documentation recommends run time check instead.

> Since I want to keep the extra warning, I am tempted to just replace
> AC_CHECK_FILE with some portable shell code.

Done. Still I doubt this warning is really useful. Most users install GiNaC
from the tarball, and don't need to even know what bison or flex is.


Best regards,
	Alexei