How exactly to do this with chdkptp? Trying to debug ixus175_elph180 filewrite failure.
What I meant in that thread was
1) Look up the address of MakeDirectory_Fut in stubs_entry.S (or stubs_entry_2.S if defined there)
=return call_func_ptr(... the address you got above...,"A/TESTDIR",-1)
where A/TESTDIR could be any valid path that doesn't exist. Native calls must be enabled in the CHDK menu to use call_func_ptr.
However, the above was specifically to check the return value. If the stub were wrong, regular os.mkdir in chdk Lua would crash or fail. You can use the llibtst.lua script in CHDK/SCRIPTS/TEST to test this and many other functions.