Bug#1096652: freefem++: ftbfs with GCC-15

[Matthias Klose]

Package: src:freefem++
Version: 4.14+dfsg-1
Severity: important
Tags: sid forky
User: debian-gcc at lists.debian.org
Usertags: ftbfs-gcc-15

[This bug is NOT targeted to the upcoming trixie release]

Please keep this issue open in the bug tracker for the package it
was filed for.  If a fix in another package is required, please
file a bug for the other package (or clone), and add a block in this
package. Please keep the issue open until the package can be built in
a follow-up test rebuild.

The package fails to build in a test rebuild on at least amd64 with
gcc-15/g++-15, but succeeds to build with gcc-14/g++-14. The
severity of this report will be raised before the forky release.

The full build log can be found at:
http://qa-logs.debian.net/2025/02/16/amd64exp/freefem++_4.14+dfsg-1_unstable_gccexp.log.gz
The last lines of the build log are at the end of this report.

To build with GCC 15, either set CC=gcc-15 CXX=g++-15 explicitly,
or install the gcc, g++, gfortran, ... packages from experimental.

  apt-get -t=experimental install g++ 

GCC 15 now defaults to the C23/C++23 standards, exposing many FTBFS.
Other Common build failures are new warnings resulting in build failures
with -Werror turned on, or new/dropped symbols in Debian symbols files.
For other C/C++ related build failures see the porting guide at
http://gcc.gnu.org/gcc-15/porting_to.html

[...]
      |                                                 ~~~~~~~~~~~~~~~~~~^~
In member function ‘bool C_F0::MeshIndependent() const’,
    inlined from ‘void Fem2D::AssembleBilinearForm(Stack, const MeshL&, const FESpaceL&, const FESpace&, bool, MatriceMap<R>&, const FormBilinear*, int*) [with R = double]’ at problem.cpp:4817:64:
AFunction.hpp:709:67: warning: ‘this’ pointer is null [-Wnonnull]
  709 |   bool MeshIndependent() const { return f ==0 ? f->MeshIndependent() : false;}
      |                                                 ~~~~~~~~~~~~~~~~~~^~
In member function ‘bool C_F0::MeshIndependent() const’,
    inlined from ‘void Fem2D::AssembleBilinearForm(Stack, const MeshL&, const FESpaceL&, const FESpaceL&, bool, MatriceMap<R>&, const FormBilinear*, int*) [with R = std::complex<double>]’ at problem.cpp:4700:65:
AFunction.hpp:709:67: warning: ‘this’ pointer is null [-Wnonnull]
  709 |   bool MeshIndependent() const { return f ==0 ? f->MeshIndependent() : false;}
      |                                                 ~~~~~~~~~~~~~~~~~~^~
In member function ‘bool C_F0::MeshIndependent() const’,
    inlined from ‘void Fem2D::AssembleBilinearForm(Stack, const MeshL&, const FESpaceL&, const FESpaceL&, bool, MatriceMap<R>&, const FormBilinear*, int*) [with R = double]’ at problem.cpp:4700:65:
AFunction.hpp:709:67: warning: ‘this’ pointer is null [-Wnonnull]
  709 |   bool MeshIndependent() const { return f ==0 ? f->MeshIndependent() : false;}
      |                                                 ~~~~~~~~~~~~~~~~~~^~
In member function ‘bool C_F0::MeshIndependent() const’,
    inlined from ‘void Fem2D::AssembleBilinearForm(Stack, const MeshL&, const FESpaceL&, const FESpaceL&, bool, MatriceCreuse<R>&, const FormBilinear*, int*) [with R = double]’ at problem.cpp:1840:65:
AFunction.hpp:709:67: warning: ‘this’ pointer is null [-Wnonnull]
  709 |   bool MeshIndependent() const { return f ==0 ? f->MeshIndependent() : false;}
      |                                                 ~~~~~~~~~~~~~~~~~~^~
In member function ‘bool C_F0::MeshIndependent() const’,
    inlined from ‘void Fem2D::AssembleBilinearForm(Stack, const Mesh&, const FESpace&, const FESpace&, bool, MatriceCreuse<R>&, const FormBilinear*, int*) [with R = double]’ at problem.cpp:915:61:
AFunction.hpp:709:67: warning: ‘this’ pointer is null [-Wnonnull]
  709 |   bool MeshIndependent() const { return f ==0 ? f->MeshIndependent() : false;}
      |                                                 ~~~~~~~~~~~~~~~~~~^~
In member function ‘bool C_F0::MeshIndependent() const’,
    inlined from ‘void Fem2D::AssembleBilinearForm(Stack, const GFESpace<Mesh3>::Mesh&, const FESpace3&, const FESpace3&, bool, MatriceCreuse<R>&, const FormBilinear*, int*) [with R = double]’ at problem.cpp:1231:61:
AFunction.hpp:709:67: warning: ‘this’ pointer is null [-Wnonnull]
  709 |   bool MeshIndependent() const { return f ==0 ? f->MeshIndependent() : false;}
      |                                                 ~~~~~~~~~~~~~~~~~~^~
In member function ‘bool C_F0::MeshIndependent() const’,
    inlined from ‘void Fem2D::AssembleBilinearForm(Stack, const MeshS&, const FESpaceS&, const FESpaceS&, bool, MatriceCreuse<R>&, const FormBilinear*, int*) [with R = double]’ at problem.cpp:1555:61:
AFunction.hpp:709:67: warning: ‘this’ pointer is null [-Wnonnull]
  709 |   bool MeshIndependent() const { return f ==0 ? f->MeshIndependent() : false;}
      |                                                 ~~~~~~~~~~~~~~~~~~^~
In member function ‘bool C_F0::MeshIndependent() const’,
    inlined from ‘void Fem2D::AssembleBilinearForm(Stack, const Mesh&, const FESpace&, const FESpace&, bool, MatriceCreuse<R>&, const FormBilinear*, int*) [with R = std::complex<double>]’ at problem.cpp:915:61:
AFunction.hpp:709:67: warning: ‘this’ pointer is null [-Wnonnull]
  709 |   bool MeshIndependent() const { return f ==0 ? f->MeshIndependent() : false;}
      |                                                 ~~~~~~~~~~~~~~~~~~^~
In member function ‘bool C_F0::MeshIndependent() const’,
    inlined from ‘void Fem2D::AssembleBilinearForm(Stack, const GFESpace<Mesh3>::Mesh&, const FESpace3&, const FESpace3&, bool, MatriceCreuse<R>&, const FormBilinear*, int*) [with R = std::complex<double>]’ at problem.cpp:1231:61:
AFunction.hpp:709:67: warning: ‘this’ pointer is null [-Wnonnull]
  709 |   bool MeshIndependent() const { return f ==0 ? f->MeshIndependent() : false;}
      |                                                 ~~~~~~~~~~~~~~~~~~^~
In member function ‘bool C_F0::MeshIndependent() const’,
    inlined from ‘void Fem2D::AssembleBilinearForm(Stack, const MeshS&, const FESpaceS&, const FESpaceS&, bool, MatriceCreuse<R>&, const FormBilinear*, int*) [with R = std::complex<double>]’ at problem.cpp:1555:61:
AFunction.hpp:709:67: warning: ‘this’ pointer is null [-Wnonnull]
  709 |   bool MeshIndependent() const { return f ==0 ? f->MeshIndependent() : false;}
      |                                                 ~~~~~~~~~~~~~~~~~~^~
In member function ‘bool C_F0::MeshIndependent() const’,
    inlined from ‘void Fem2D::AssembleBilinearForm(Stack, const MeshL&, const FESpaceL&, const FESpaceL&, bool, MatriceCreuse<R>&, const FormBilinear*, int*) [with R = std::complex<double>]’ at problem.cpp:1840:65:
AFunction.hpp:709:67: warning: ‘this’ pointer is null [-Wnonnull]
  709 |   bool MeshIndependent() const { return f ==0 ? f->MeshIndependent() : false;}
      |                                                 ~~~~~~~~~~~~~~~~~~^~
make[6]: Leaving directory '/build/reproducible-path/freefem++-4.14+dfsg/src/fflib'
make[5]: *** [Makefile:667: all] Error 2
make[5]: Leaving directory '/build/reproducible-path/freefem++-4.14+dfsg/src/fflib'
make[4]: *** [Makefile:556: all-recursive] Error 1
make[4]: Leaving directory '/build/reproducible-path/freefem++-4.14+dfsg/src'
make[3]: *** [Makefile:814: all-recursive] Error 1
make[3]: Leaving directory '/build/reproducible-path/freefem++-4.14+dfsg'
make[2]: *** [Makefile:764: all] Error 2
make[2]: Leaving directory '/build/reproducible-path/freefem++-4.14+dfsg'
dh_auto_build: error: make -j8 returned exit code 2
make[1]: *** [debian/rules:20: override_dh_auto_build] Error 25
make[1]: Leaving directory '/build/reproducible-path/freefem++-4.14+dfsg'
make: *** [debian/rules:9: binary] Error 2
dpkg-buildpackage: error: debian/rules binary subprocess returned exit status 2