--- libsmb/libsmbclient.o ---
cc-1515 c99: WARNING File = libsmb/libsmbclient.c, Line = 6019
A value of type "void *" cannot be assigned to an entity of type
context->internal->_auth_fn_with_context = option_value;
Fixed by check-in 16550 (in Samba3 branch) and 16551 (in trunk). Thanks for the report!
I've fixed it by replacing the casts to the various types with use of variable argument lists to always obtain the correct type. This is now legal C, so should compile without error. Please let me know if you still see any problems.