On Thu, Sep 8, 2011 at 11:29 AM, Jeffrey Lee Hellrung, Jr. <jeffrey.hellrung@gmail.com> wrote:
On Thu, Sep 8, 2011 at 7:46 AM, Jared McKee <jared.mckee@gmail.com> wrote:
On Thu, Sep 8, 2011 at 10:19 AM, Jeffrey Lee Hellrung, Jr. <jeffrey.hellrung@gmail.com> wrote:
On Wed, Sep 7, 2011 at 7:48 PM, Jared McKee <jared.mckee@gmail.com>
wrote:
I would like to determine interest in a possible library submission.
I have written some code which converts a member function and object pointer combination to a free function for use in C style callbacks. It has
some
limitations which I will describe shortly.
The basic idea is to be able to convert:
R (B::*)(T0,T1,…) and B*
to
R (*)(T0,T1,…)
Here's an example usage:
class foo { int x; int test(int v) {return x + v;} };
foo* a = new foo; a->x = 3; int (*f)(int) = delegate(a, &foo::inc); cout << f(4) << endl; // outputs "7"
[...snip implementation notes...]
I admit I only glossed over your implementation notes, but it looks like this would be very similar to (or...the same as...?) a bound (e.g., via Boost.Bind) boost::mem_fn:
http://www.boost.org/doc/libs/1_47_0/libs/bind/mem_fn.html
Is that accurate?
Good question. I believe the approach in boost::mem_fn is to create C++ functor objects which are structs with operator() overloaded. These functors are not compatible with straight C function pointers. My implementation returns C function pointers, not functors.
Here's a discussion about the topic:
http://stackoverflow.com/questions/1840029/passing-functor-as-function-point...
Oh...dear.
I can see the use for a small module that converts C++ functors into a kind of (function pointer, void*) struct for use with interfacing with C-style APIs, but trying to get a lonely function pointer to call a functor seems wrought with peril (e.g., "gotchas" and safety issues)... I assume you're trying to provide a general solution to the 3rd case within the first answer to the referenced stackoverflow link?
That's exactly right.
- Jeff
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