[Tinycc-devel] vararg compilation bug

[Marcus Ramse]

Hello!

This is my first email to a mailing list so apologies if anything looks 
strange.

It seems I have discovered a bug in TCCs compilation of varargs.

I'm on "tcc version 0.9.27 (x86_64 Linux)".

Please see the following code:

- - - - -

#include <stdio.h>
#include <stdarg.h>

struct test {
    void *foo, *bar, *baz;
};

struct test example(int a, int b, ...)
{
    va_list va;
    va_start(va, b);
    printf("a: %d, b: %d, va_arg: %d\n", a, b, va_arg(va, int));
    va_end(va);
    return (struct test) {};
}

int main()
{
    example(1, 2, 3);
    return 0;
}

- - - - -

$ tcc -run example.c

a: 1, b: 2, va_arg: 2

- - - - -

GCC and Clang both give "va_arg: 3" which is what I'd expect from this 
code.

It seems to happen when returning a non-trivial struct from the function 
which has varargs.


Thanks for reading,

Marcus