Re: [Tinycc-devel] vararg compilation bug

[Christian Jullien]

Hi,

I confirm that this issue also exists with mob (which now displays git short 
hash):

[jullien@fedora64 ~]$ tcc -v
tcc version 0.9.27 - 035ae7d (x86_64 Linux)

-----Original Message-----
From: Tinycc-devel [mailto:tinycc-devel-bounces+eligis=orange.fr@nongnu.org] On 
Behalf Of Marcus Ramse
Sent: Sunday, April 11, 2021 05:51
To: tinycc-devel@nongnu.org
Subject: [Tinycc-devel] vararg compilation bug

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


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