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

FILE *log_func_call;
/* The code dynamically generated can't get access to variable, must provide a
 * function. */
FILE *get_log_func_call() {
    return log_func_call;
}

typedef int (*func_t)(int arg);

int foo(int a) {
    return a + 1;
}

char wrap[] =
    "int wrapped(int arg) {"
    "    int val = origin(arg);"
    "    printf(\"Inside wrapped function\n\");"
    "    fprintf(get_log_func_call(), \"arg: %d ret: %d\n\", arg, val);"
    "    return val;"
    "}";

func_t create_wrap_function(func_t origin) {
    TCCState *s;
    func_t func = func;
    void *mem;
    int size;

    s = tcc_new();
    if (!s) {
        fprintf(stderr, "Could not create tcc state\n");
        exit(1);
    }

    /* MUST BE CALLED before any compilation */
    tcc_set_output_type(s, TCC_OUTPUT_MEMORY);

    if (tcc_compile_string(s, wrap) == -1)
        exit(1);

    /* as a test, we add a symbol that the compiled program can use.
       You may also open a dll with tcc_add_dll() and use symbols from that */
    tcc_add_symbol(s, "get_log_func_call", get_log_func_call);
    tcc_add_symbol(s, "origin", origin);

    /* get needed size of the code */
    size = tcc_relocate(s, NULL);
    if (size == -1)
        exit(1);

    /* allocate memory and copy the code into it */
    mem = malloc(size);
    tcc_relocate(s, mem);

    /* get entry symbol */
    func = tcc_get_symbol(s, "wrapped");
    if (!func) {
       fprintf(stderr, "can't get function entry\n");
       exit(1);
    }

    /* delete the state */
    tcc_delete(s);

    return func;
}

int main(int argc, char* argv[]) {
    assert(log_func_call = fopen("log_func_call", "w"));
    func_t bar = create_wrap_function(foo);
    printf("%d\n", bar(2));

    return 0;
}