Re: [Tinycc-devel] Miscompilation returning small struct

[Steffen Nurpmeso]

tinycc-devel@nongnu.org wrote in
 <47c96f8b-130b-c0b7-79f2-a33e132563cf@ludocode.com>:
 |I've encountered what I believe is a miscompilation bug in TinyCC. \
 |I'm using
 |tcc 0.9.27 on latest Arch Linux on x86_64. I can't reproduce the same \
 |issue on
 |the mob branch so this may already be fixed, but I can't find a bug report
 |about anything similar so it may just be a coincidence; the bug might \
 |still be
 |around, just reproducible in a different way. I tried reducing the \
 |code as much
 |as possible:
 |
 |     #include <stdint.h>
 |     #include <stdio.h>
 |
 |     typedef struct coords_t {
 |         uint8_t x, y;
 |     } coords_t;
 |
 |     typedef struct list_t {
 |         void* context;
 |         coords_t head;
 |         coords_t tail;
 |     } list_t;
 |
 |     static coords_t list_head(list_t* list) {
 |         return list->head;
 |     }
 |
 |     int main(void) {
 |         list_t list;
 |         list.tail.x = 17;
 |         list.tail.y = 23;
 |
 |         coords_t bob = {3, 4};
 |         coords_t alice = {2, 1};
 |         coords_t eve = {1, 0};
 |
 |         printf("%u:%u\n", eve.x, eve.y);
 |         list_head(&list); // ignored return value, should be no-op
 |         printf("%u:%u\n", eve.x, eve.y);
 |     }
 |
 |The code prints the contents of a struct before and after a no-op function
 |call. The output should be the same. Under GCC, Clang and chibicc it prints
 |this:
 |
 |     1:0
 |     1:0
 |
 |Under TinyCC it prints this:
 |
 |     1:0
 |     17:23

I cannot reproduce this with
e5c3d1dc705f4c1b4ecccf795f97fa409914ea2e from January 4th.  Damned
U+00A0 whitespace ;P

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)