[petsc-users] Inquiry about issue when compiling with clang

[Jed Brown]

I'm assuming that you configured and built PETSc with gcc, and now are building a package that depends on PETSc using AOCC? Is it possible to configure PETSc with the same compiler, or to use -std=gnu++17 (any dialect that supports GNU extensions)?

Benjamin Chapman via petsc-users <petsc-users at mcs.anl.gov> writes:

> Hello,
>
> We are using PETSc as part of a larger project and are switching from compiling with gcc to using AOCC (clang). However, I am getting an error from my include statements stating that the data type __complex128 is an "unknown type name". The full error log is attached.
>
> I found this solution online (FreeFem - PETSc compilation error - libblas.a/liblapack.a cannot be used - FreeFEM installation - FreeFEM<https://urldefense.us/v3/__https://community.freefem.org/t/freefem-petsc-compilation-error-libblas-a-liblapack-a-cannot-be-used/2771/8__;!!G_uCfscf7eWS!fqL9KO-Su4o3uzl3iGDcskkh1utILAAeNaaZ25v6yAZ2CEn2axOiqwOCYwJHMlq_jQwt9Oc4FXRaM9tMvfMBVx5mCetoylgskpID89ee$ >), which says to comment out a line in the petscconf.h header file. Is this a safe fix or is there a more elegant way to go about this?
>
> Best,
> Ben
> [ 64%] Building CXX object src/CMakeFiles/rebel_lib.dir/common/coordinate_system.cpp.o
> [ 65%] Building CXX object src/CMakeFiles/rebel_lib.dir/common/FFTW_interface.cpp.o
> [ 65%] Building CXX object src/CMakeFiles/rebel_lib.dir/common/fileIO.cpp.o
> [ 66%] Building CXX object src/CMakeFiles/rebel_lib.dir/common/lapacke_interface.cpp.o
> [ 66%] Building CXX object src/CMakeFiles/rebel_lib.dir/common/petsc_extensions.cpp.o
> In file included from /mnt/scratch/bchapman/rebel/src/common/petsc_extensions.cpp:7:
> In file included from /mnt/scratch/bchapman/rebel/src/common/petsc_extensions.h:14:
> In file included from /mnt/scratch/bchapman/rebel/build/external/builds/petsc-3.21.0/include/petscksp.h:6:
> In file included from /mnt/scratch/bchapman/rebel/build/external/builds/petsc-3.21.0/include/petscpc.h:6:
> In file included from /mnt/scratch/bchapman/rebel/build/external/builds/petsc-3.21.0/include/petscmat.h:6:
> In file included from /mnt/scratch/bchapman/rebel/build/external/builds/petsc-3.21.0/include/petscvec.h:8:
> In file included from /mnt/scratch/bchapman/rebel/build/external/builds/petsc-3.21.0/include/petscsys.h:193:
> /mnt/scratch/bchapman/rebel/build/external/builds/petsc-3.21.0/include/petscmath.h:429:45: error: unknown type name '__complex128'
>   429 | PETSC_EXTERN MPI_Datatype MPIU___COMPLEX128 MPIU___COMPLEX128_ATTR_TAG;
>       |                                             ^
> /mnt/scratch/bchapman/rebel/build/external/builds/petsc-3.21.0/include/petscmath.h:424:71: note: expanded from macro 'MPIU___COMPLEX128_ATTR_TAG'
>   424 |       #define MPIU___COMPLEX128_ATTR_TAG PETSC_ATTRIBUTE_MPI_TYPE_TAG(__complex128)
>       |                                                                       ^
> /mnt/scratch/bchapman/rebel/src/common/petsc_extensions.cpp:2570:13: warning: decomposition declarations are a C++17 extension [-Wc++17-extensions]
>  2570 |         const auto [min, max] = std::minmax_element(std::begin(s), std::end(s));
>       |                    ^~~~~~~~~~
> 1 warning and 1 error generated.
> make[2]: *** [src/CMakeFiles/rebel_lib.dir/build.make:132: src/CMakeFiles/rebel_lib.dir/common/petsc_extensions.cpp.o] Error 1
> make[1]: *** [CMakeFiles/Makefile2:772: src/CMakeFiles/rebel_lib.dir/all] Error 2
> make: *** [Makefile:136: all] Error 2