RE: AC_CONFIG_LINKS and MSVC

[David Byron]

On Fri, Apr 14, 2006, Noah Misch wrote: 

> You can use the third argument to AC_CONFIG_COMMANDS to get
> the variable declared in `config.status'.  Probably this:
> 
>   AC_CONFIG_COMMANDS(foo, $config_cmd, config_cmd='$config_cmd')

This did the trick.

> AC_CONFIG_LINKS is not so widely used, and neither is
> `cccl', so it is possible that you are the first person to
> face this problem.

This isn't just a cccl problem, but a problem for anyone using MSVC.  I
guess using autoconf with MSVC pretty much implies cccl, but just in
case.

> I would use your essential approach involving
> AC_CONFIG_COMMANDS, but rather than checking $host to decide
> whether to use symbolic links for headers, write a
> behavioral test.  Namely, create a simple header file, make
> a symbolic link to the header, and try to compile a program
> that includes it by its symlinked name.  If this succeeds,
> use `ln -s' or `$as_ln_s'; otherwise, use `cp -p'.

Good point.  Changing topics a bit, the reason I have a hard coded host
check is that

AC_C_BIGENDIAN(ENDIAN=be,ENDIAN=le)

doesn't work for me using MSVC.  The test program #includes sys/params.h
which MSVC can't find.  config.log has:

conftest.c(33) : fatal error C1083: Cannot open include file:
'sys/param.h': No such file or directory 

It happens to choose little endian but I didn't want to depend on that.

> > Does it make sense to have the code that supports
> > AC_CONFIG_LINKS use $as_ln_s instead of straight ln -s in:
> > 
> >   # Try a symlink, then a hard link, then a copy.
> >   ln -s $ac_rel_source $ac_dest 2>/dev/null ||
> >     ln $srcdir/$ac_source $ac_dest 2>/dev/null ||
> >     cp -p $srcdir/$ac_source $ac_dest ||
> 
> That is probably a reasonable clean up.  It will not fix
> your problem, because there is no clean way to override
> $as_ln_s in `config.status'.

As I think about this more, creating some links is OK.  It's only those
that MSVC ends up using that cause trouble.  Not sure if there are
enough of them that a special AC_CONFIG_LINK_DO_THE_RIGHT_THING macro is
worth it.

Thanks for your help.

-DB