Choose the method used to find the roots in the GC. This only applies to our framework GCs. You have a choice of two alternatives: - ``--gcrootfinder=shadowstack``: use a so-called "shadow stack", which is an explicitly maintained custom stack of root pointers. This is the most portable solution. - ``--gcrootfinder=asmgcc``: use assembler hackery to find the roots directly from the normal stack. This is a bit faster, but platform specific. It works so far with GCC or MSVC, on i386 and x86-64. It is tested only on Linux (where it is the default) so other platforms (as well as MSVC) may need various fixes before they can be used. You may have to force the use of the shadowstack root finder if you are running into troubles or if you insist on translating PyPy with other compilers like clang.