dlopen sets up some thread-local state that isn't cleaned up by
`dlclose`. Additionally, now that we're linking against different
versions of libssh2 and OpenSSL, we're seeing different leak signatures.
valgrind will warn that OpenSSL will use undefined data in connect/read
when talking to certain other TLS stacks. Thankfully, this only seems
to occur when gcc is the compiler, so hopefully valgrind is just
misunderstanding an optimization. Regardless, suppress this warning.
On Ubuntu, the combination of libgcrypt and libssh2 is quite old and
known to contain memory leaks. We thus have several functions listed in
our suppressions file that are known to leak. Due to a recent update of
libssh2 or libgcrypt, there now are new memory leaks caused by
libssh2_session_handshake and libssh2_init that cause the CI to fail.
Add a new suppression to fix the issue.
Right now, we have an awful hack in our test CI setup that extracts the
test command from CTest's output and then prepends the leak checker.
This is dependent on non-machine-parseable output from CMake and also
breaks on various ocassions, like for example when we have spaces in the
current path or when the path contains backslashes. Both conditions may
easily be triggered on Win32 systems, and in fact they do break our
Azure Pipelines builds.
Remove the awful hack in favour of a new CMake build option
"USE_LEAK_CHECKER". If specifying e.g. "-DUSE_LEAK_CHECKER=valgrind",
then we will set up all tests to be run under valgrind. Like this, we
can again simply execute ctest without needing to rely on evil sourcery.
