Boost Filesystem fails to copy between volumes. Consider replacing with std::filesystem.

[jmpf]

Describe the bug
Boost Filesystem fails to copy between volumes. This is a known Boost bug: https://stackoverflow.com/questions/24209886/invalid-cross-device-link-error-with-boost-filesystem

To Reproduce
This may be specific to Boost 1.74.0 with /tmp and /home on different volumes:

jmpf@csu15256:~/Workspace/Chaste/build$ df /tmp/
Filesystem     1K-blocks      Used Available Use% Mounted on
/dev/nvme0n1p2 490617784 404090124  61532180  87% /
jmpf@csu15256:~/Workspace/Chaste/build$ df /home
Filesystem     1K-blocks      Used Available Use% Mounted on
/dev/nvme1n1p1 491133848 330703932 135408220  71% /home

ctest -VV -R TestFileFinder
...
13: Entering TestFindMatches
13: Passed
13: Entering TestCopying
13: 
13: /home/jmpf/Workspace/Chaste/global/test/TestFileFinder.hpp:362: Error: Test failed: 
13: Chaste error: ./global/src/FileFinder.cpp:332: boost::filesystem::copy_file: Invalid cross-device link: "/home/jmpf/Workspace/Chaste/global/test/TestFileFinder.hpp", "/tmp/jmpf/testoutput/TestFileFinder_TestCopying/TestFileFinder.hpp"
13: Failed
13: Entering TestDefaultConstructor
13: Passed

Workaround
Change environment variable to give a different output location

export CHASTE_TEST_OUTPUT="/home/jmpf/tmp-chaste/"

Expected behaviour
Test should pass

System
Please provide relevant details of your system, such as:

• OS version: Ubuntu 22.04
• Relevant Chaste dependency versions Boost: libboost-filesystem-dev:amd64 1.74.0.3ubuntu7

[jmpf]

We currently use -std=c++14 for compiling Chaste.

It's not clear if all the versions of C++ compilers in use will support the std::filesystem. Probably they all will but some may need #include <experimental/filesystem> rather than #include <filesystem> .

jmpf@csu15256:~$ cat temp.cc
#include <filesystem>
namespace fs=std::filesystem;

int main(){}
jmpf@csu15256:~$ g++ -std=c++17 temp.cc 
jmpf@csu15256:~$ g++ -std=c++14 temp.cc 
temp.cc:2:19: error: ‘filesystem’ is not a namespace-name
    2 | namespace fs=std::filesystem;
      |                   ^~~~~~~~~~

[mirams]

Any problem with going straight to compiling with c++17 ? I've forgotten if we have a 'policy' on that move @fcooper8472 ?

[jmpf]

@mirams How many of our users are using C++ compilers that cannot handle C++17?

[mirams]

our what?

[jmpf]

See also #107 -- There's now a compelling reason to switch on C++17 features.

[jmpf]

Will make https://github.com/Chaste/Chaste/tree/issue_100 into pull request when we're green

[jmpf]

Fixed by #115