tinyc compiler - libtcc, how to bound check? - c

Question

im using libtcc to compile c code on the fly. Im going to use it on a cloud computer, to be used over the internet.
how do i use tinyc's built in memory and bound checker function?
heres an example that comes with the tinyc libtcc library?
any help would be great!
thank you!
/*
* Simple Test program for libtcc
*
* libtcc can be useful to use tcc as a "backend" for a code generator.
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "libtcc.h"
/* this function is called by the generated code */
int add(int a, int b)
{
return a + b;
}
char my_program[] =
"int fib(int n)\n"
"{\n"
" if (n <= 2)\n"
" return 1;\n"
" else\n"
" return fib(n-1) + fib(n-2);\n"
"}\n"
"\n"
"int foo(int n)\n"
"{\n"
" printf(\"Hello World!\\n\");\n"
" printf(\"fib(%d) = %d\\n\", n, fib(n));\n"
" printf(\"add(%d, %d) = %d\\n\", n, 2 * n, add(n, 2 * n));\n"
" return 0;\n"
"}\n";
int main(int argc, char **argv)
{
TCCState *s;
int (*func)(int);
void *mem;
int size;
s = tcc_new();
if (!s) {
fprintf(stderr, "Could not create tcc state\n");
exit(1);
}
/* if tcclib.h and libtcc1.a are not installed, where can we find them */
if (argc == 2 && !memcmp(argv[1], "lib_path=",9))
tcc_set_lib_path(s, argv[1]+9);
/* MUST BE CALLED before any compilation */
tcc_set_output_type(s, TCC_OUTPUT_MEMORY);
if (tcc_compile_string(s, my_program) == -1)
return 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, "add", add);
/* get needed size of the code */
size = tcc_relocate(s, NULL);
if (size == -1)
return 1;
/* allocate memory and copy the code into it */
mem = malloc(size);
tcc_relocate(s, mem);
/* get entry symbol */
func = tcc_get_symbol(s, "foo");
if (!func)
return 1;
/* delete the state */
tcc_delete(s);
/* run the code */
func(32);
free(mem);
return 0;
}

Answer 1

you can set bounds checking manually using:
s->do_bounds_check = 1; //s here is TCCState*
just make sure libtcc is compiled with CONFIG_TCC_BCHECK being defined.
you may also want to enable debugging using:
s->do_debug = 1;
the command line option -b does the exact same to enable bounds checking (it enables debugging as well).