OpenFOAM cannot be compiled with gcc 13

Summary

From gcc version 13 and onwards, it is required to #include <cstdint> to have access to types such as uint64_t. OpenFOAM and third-party libraries needs to be patched to allow compilation with gcc 13.

This applies to a lot of projects, for example here is the corresponding issue for VTK.

This is described also in the gcc 13 porting guide .

Steps to reproduce

Trying to compile OpenFOAM v2212 with gcc 13 on my Arch Linux box results in the following error, already in third party libraries (kahip):

error: ‘uint64_t’ in namespace ‘std’ does not name a type; did you mean ‘wint_t’?

Workarounds

I have tried setting the C++ standard by exporting FOAM_EXTRA_CXXFLAGS=--std=c++11, and can confirm this is picked up by the compiler, but this does not address the issue.

So far I have only been able to compile using an older gcc version, e.g. by setting "version=12" in the WM_COMPILE_CONTROL variable in etc/bashrc before sourcing.