Short ans: Please read previous question first; this is a corollary.
Long ans: In C++, member fns have an implicit parameter which points to the object (the 'this' ptr inside the member fn). Normal C fns can be thought of as having a different calling convention from member fns, so the types of their ptrs (ptr-to-member-fn vs ptr-to-fn) are different and incompatible. C++ introduces a new type of ptr, called a ptr-to-member, which can only be invoked by providing an object (see ARM 5.5). Do NOT attempt to 'cast' a ptr-to-mem-fn into a ptr-to-fn; the result is undefined and probably disastrous; a ptr-to- member-fn is NOT required to contain the machine addr of the appropriate fn (see ARM, 8.1.2c, p.158). As was said in the last example, if you want a regular C fn ptr, use either a top-level (non-class) fn, or a 'static' (class) member fn.
