A first experiment in creating and running x86 machine code on the fly. By Nick Desaulniers: http://nickdesaulniers.github.io/blog/2013/04/03/basic-jit/

rawcode.c

// To compile this on mac: gcc -m32 -o rawcode rawcode.c
// Probably the same on linux, or drop the -m32.
// Then: ./rawcode

#include <stdio.h> // printf
#include <string.h> // memcpy
#include <sys/mman.h> // mmap, munmap

int main () {
    // x86 machine code for: int mul (int a, int b) { return a * b; }
    unsigned char code [] = {
        0x55,                    // push %ebp
        0x89, 0xe5,              // mov  %esp,%ebp
        0x8b, 0x45, 0x08,        // mov  0x8(%ebp),%eax
        0x0f, 0xaf, 0x45, 0x0c,  // imul 0xc(%ebp),%eax
        0x5d,                    // pop  %ebp
        0xc3                     // ret
    };

    // allocate executable memory via sys call
    void* mem = mmap(NULL, sizeof(code), PROT_WRITE | PROT_EXEC,
                     MAP_ANON | MAP_PRIVATE, -1, 0);

    // copy runtime code into allocated memory
    memcpy(mem, code, sizeof(code));

    // typecast allocated memory to a function pointer
    int (*func) () = mem;

    // call function pointer
    printf("19 * 11 = %d\n", func(19, 11));

    // free up allocated memory
    munmap(mem, sizeof(code));
}