void* is literally float, how to cast?

Question

So I\'m using this C library in my C++ app, and one of the functions returns a void*. Now I\'m not the sharpest with pure C, but have heard that a void* can be cast to prett

Answer 1

Try using pointers:

void *theValueAsVoidPtr = // whatever

float flt = *(float *)&theValueAsVoidPtr;

Answer 2

If I understand correctly, your library is returning a float value in a variable whose declared type is void *. The safest way to get it back out again is with a union:

#include <assert.h>
static_assert(sizeof(float) == sizeof(void *));

union extract_float {
    float vf;
    void * vp;
};

float foo(...)
{
    union extract_float ef;
    ef.vp = problematic_library_call(...);
    return ef.vf;
}

Unlike the approach in the accepted answer, this does not trigger undefined behavior.