Re: [pushed/v2 1/9] gdb/configure: Add --with-libgmp-prefix option

[Bernd Edlinger <bernd.edlinger@hotmail.de>]

On 11/16/20 4:45 AM, Joel Brobecker wrote:
> Hi Bernd,
> 
>> I noticed that this does not allow to build gmp in-tree like it is
>> possible for gcc.  I tried to overcome this by the attached patch.
> 
> Indeed. It's not something I had considered.
> 
>> While doing so, I also noticed an incompatibility with the top level
>> configure stript, which advertises, and passes -with-gmp-include
>> and -with-gmp-lib if in-tree gmp is found.
>>
>> So the --with-libgmp-prefix is not that the top level configure
>> script suggests:
>>
>> $ ./configure --help | grep gmp
>>   --with-gmp-dir=PATH     this option has been REMOVED
>>   --with-gmp=PATH         specify prefix directory for the installed GMP
>>                           --with-gmp-include=PATH/include plus
>>                           --with-gmp-lib=PATH/lib
>>   --with-gmp-include=PATH specify directory for installed GMP include files
>>   --with-gmp-lib=PATH     specify directory for the installed GMP library
>>
>> What do you think, can we allow these traditional configure options
>> additional to the new --with-libgmp-prefix?
> 
> Can you check if these options are actually used elsewhere in
> the binutils-gdb project? The idea I have in the back of my mind
> is to see whether we can use the same options as the ones we've been
> using in GDB or not. The fact that we have an AC_LIB_HAVE_LINKFLAGS
> macro which takes care of handling dependencies for us tells me
> that we are transitioning away from the model above where we add
> the options "by hand" in configure.ac, and instead rely on the new
> macro.
> 

I think they are also used as configuration options in mpfr
and mpc, and understood by the top level configuration.

$ mpc-1.0.3/configure --help
[...]
  --with-mpfr-include=DIR MPFR include directory
  --with-mpfr-lib=DIR     MPFR lib directory
  --with-mpfr=DIR         MPFR install directory
  --with-gmp-include=DIR  GMP include directory
  --with-gmp-lib=DIR      GMP lib directory
  --with-gmp=DIR          GMP install directory
[...]
$
[...]
  --with-gmp-include=DIR  GMP include directory
  --with-gmp-lib=DIR      GMP lib directory
  --with-gmp=DIR          GMP install directory
  --with-gmp-build=DIR    GMP build directory (please read INSTALL file)
[...]


> One thing I did note is that GDB has some options for MPFR support
> and in particular, it has --with-mpfr:
> 
>   --with-mpfr             include MPFR support (auto/yes/no)
> 
> As you can see, the --with-gmp option you propose is not consistent
> with the above.
> 

Hmm, yes, indeed, the --with-mpfr seems to be hand-crafted, since there is
currently no --with-gmp=[auto/yes/no], (neither before or after my patch).
I think the --with-mpfr might probably cause problems with mpc in-tree build,
if that ever happens.

Of course the this mpfr support does not work with in-tree mpfr either.
For that to work we would need at minimum --with-mpfr-include=DIR and
--with-mpfr-lib=DIR or equivalent, however mpfr is probably not worth the effort.


> Unfortunately, in digging further, I found that toplevel configure
> *also* has --with-mpfr, with a different meaning:
> 
>   --with-mpfr=PATH        specify prefix directory for installed MPFR package.
>                           Equivalent to --with-mpfr-include=PATH/include plus
>                           --with-mpfr-lib=PATH/lib
> 
> The way we expect people to configure GDB is to configure it as
> part of the binutils-gdb project, so I don't see how GDB's --with-mpfr
> could work, unless the top-level configury is more elaborate than
> I remembered.
> 
> Depending on the above, perhaps it might be better to actually
> to change the top-level configury to advertise the --with-gmp-prefix
> options instead of adding parallel support for the old-style
> options in GDB's configury. And while at it, perhaps start deprecating
> the old-style ones in the top-level configury.
> 

Of course there is still mpfr's --with-gmp=DIR configuration option.

But there may also be other surprises like this in configure.ac :

  *-*-freebsd*)
    if test "x$with_gmp" = x && test "x$with_gmp_dir" = x \
        && ! test -d ${srcdir}/gmp \
        && test -f /usr/local/include/gmp.h; then
      with_gmp=/usr/local
    fi
    ;;

as you see, this option was already there for a while.

> One more note: For me, I think we can handle the question of
> in-tree building independently of the question of the configury's
> options -- which is good, because I think the latterm might require
> a bit of discussion.
> 
>> Can we the top level Makefile.def change in binutils-gdb or has this
>> be checked-in first in gcc?
> 
> That's a good question. I *think* that binutils + GDB now have
> ownership, but I might be wrong. Hopefully others know better.
> If not, I will ask.
> 
>> 2020-11-15  Bernd Edlinger  <bernd.edlinger@hotmail.de>
>>
>> 	* Makefile.def: Prepare for GDB build with intree GMP.
>> 	* Makefile.in: Regenerate.
>>
>> gdb:
>> 2020-11-15  Bernd Edlinger  <bernd.edlinger@hotmail.de>
>>
>> 	* configure.ac: Add --with-gmp= --with-gmp-include= and --with-gmp-lib=
>> 	for compatibility with top level configure script.
>> 	* configure: Regenerate.
> 
> Looking at your patch, I'm wondering how this would all fit together...
> Would it all work automatically (like it does for libiconv, I believe),
> or where you planning on having to pass --with-gmp options ?
> 

No, all it needs, is a symlink named "gmp" pointing to gmp's source tree, in the
top level directory, like gcc's contrib/download_prerequisites does.

Once the gmp directory is there the --with-gmp-include and --with-gmp-lib options
are passed to in-tree mpfr if any, and now additionally to gdb.

The --with-gmp=DIR option itself is not needed at all for the in-tree build.


Bernd.