build problems with gcc 15

[VictorEijkhout]

Test program with

find_package( PkgConfig REQUIRED )
pkg_check_modules( P4EST REQUIRED p4est )

On one machine I get:

-- Found PkgConfig: /usr/bin/pkg-config (found version "1.7.3")
-- Checking for module 'p4est'
--   Package 'sc', required by 'p4est', not found
CMake Error at /home1/apps/cmake/4.1.1/share/cmake-4.1/Modules/FindPkgConfig.cmake:639 (message):
  The following required packages were not found:

   - p4est

Other machine:

-- Found PkgConfig: /usr/bin/pkg-config (found version "1.7.3")
-- Checking for module 'p4est'
--   Package 'p4est', required by 'virtual:world', not found
CMake Error at /home1/apps/cmake/4.1.1/share/cmake-4.1/Modules/FindPkgConfig.cmake:639 (message):
  The following required packages were not found:

   - p4est

Older versions of gcc are fine.

It looks like sc is properly installed:

/scratch/00434/eijkhout/installation/installation-p4est-2.8.7-vista-gcc15.1-openmpi5.0.8/lib/pkgconfig/libsc-0.0.0.pc
/scratch/00434/eijkhout/installation/installation-p4est-2.8.7-vista-gcc15.1-openmpi5.0.8/lib/pkgconfig/libsc-2.8.7.pc
/scratch/00434/eijkhout/installation/installation-p4est-2.8.7-vista-gcc15.1-openmpi5.0.8/lib/pkgconfig/libsc.pc
/scratch/00434/eijkhout/installation/installation-p4est-2.8.7-vista-gcc15.1-openmpi5.0.8/lib64/libsc.so
/scratch/00434/eijkhout/installation/installation-p4est-2.8.7-vista-gcc15.1-openmpi5.0.8/lib64/libsc.so.4.0.0

[tim-griesbach]

We had a look at the report and could not reproduce the issue with gcc 15 (cf. this CI test using gcc 15 and CMake). Maybe the issue is related to some setup change on your system coming with the change to gcc 15.

[VictorEijkhout]

This is the source of the problem:

[staff p4est:54] ls $TACC_P4EST_DIR
cmake/  doc/  example/  include/  lib/  lib64/  share/  src/  test/
[staff p4est:55] ls $TACC_P4EST_DIR/lib64
libp4est.so@  libp4est.so.4.0.0*  libsc.so@  libsc.so.4.0.0*
[staff p4est:56] ls $TACC_P4EST_DIR/lib
pkgconfig/

Somehow there is both a lib and lib64 directory.

Maybe this is caused by using a newer cmake? I don't know what the logic is that cmake uses to create lib/lib64 directories.

[tim-griesbach]

We could not reproduce having coexisting lib and lib64 folders, but we found places in the CMake code where we can improve the robustness of the relevant folder logic. We have one branch for p4est and one for libsc.

Could you confirm whether these branches result in your system having only a single library directory (i.e., just lib or just lib64)? Each branch should give the desired outcome for the p4est and libsc library folder, respectively.

We kept the changes split because we did not update p4est’s submodule in the experimental branch. If we move forward with incorporating this work, we would of course update the submodule accordingly.