Defer

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>

struct DeferConversionStruct{
    void **ptr;
    DeferConversionStruct(void **in)
    { ptr = in; }
    #define CreatePtrConversion(type) \
    DeferConversionStruct(type **in) \
    { ptr = (void **)in; }
    CreatePtrConversion(int)
    CreatePtrConversion(float)
    CreatePtrConversion(double)
    
};

struct DeferStruct{
    void (*function_ptr)(void *);
    void **data_ptr;
    ~DeferStruct()
    {
        assert(*data_ptr);
        function_ptr(*data_ptr);
    }
};
#define CONCAT_(a,b) a##b
#define CONCAT(a,b) CONCAT_(a,b)
#define DEFER(f_ptr_in, d_ptr_in)                       \
DeferStruct CONCAT(SomeRandomVariable,__COUNTER__) = {  \
    .function_ptr = (f_ptr_in),                         \
    .data_ptr = DeferConversionStruct{d_ptr_in}.ptr     \
}


int main() {
    
    int *a = 0;
    DEFER(&free, &a);
    
    a = (int *)malloc(31);
    
    return 0;
}