Hello,
I have recently been researching the possibility of using libtcc to make
C a highly efficient scripting language for my codebase. The idea is
certainly very promising - at a similar level of visible abstraction,
TCC takes two seconds to allocate a single-gigabyte array on my setup,
Lua takes about five... to trigger OOM :-)
However, it appears that if if I use the -rdynamic flag while compiling
the codebase, the TCC state is being given access to symbols that have
not been explicitly added to it - I've attached the code of a simple
program showcasing the issue. Because CMake exposes this flag by default
to the *nix compiler toolchains (spent quite a while scratching my
head...), this may be a fairly serious vulnerability if unnoticed.
I would therefore love to get an answer on whether the described
behavior is intentional. If it indeed is - TCC should probably get it
visibly documented for the benefit of security and easier adoption of
the library. If not - well, I've tried to fix it and failed (or rather,
succeeded while making a thousand other things break, by changing
RTLD_DEFAULT to RTLD_NEXT in tccelf.c:823), so if anybody here happened
to be blessed with actual know-how... :-)
Thank You a thousand times to all the great contributors to this
outstanding project!
- Czcibor
#include <libtcc.h>
const char* code = "#include <stdio.h> \n\
extern float add(float a, float b); \n\
int main() { \n\
printf(\"%f\\n\", add(1, 2)); \n\
return 0; \n\
}";
float add(float a, float b) {
return a + b;
}
int main() {
void* func;
TCCState *s = tcc_new();
tcc_set_output_type(s, TCC_OUTPUT_MEMORY);
//tcc_add_symbol(s, "add", (void*) add);
if(tcc_compile_string(s, code) == -1 || tcc_relocate(s, TCC_RELOCATE_AUTO) < 0 || !(func = tcc_get_symbol(s, "main"))) {
tcc_delete(s);
return 1;
}
((int (*)()) func)();
//build with tcc seetcc.c -rdynamic -Wall -ldl -ltcc
//expected output: tcc: error: undefined symbol 'add'
//actual output: 3.000000
tcc_delete(s);
return 0;
}
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