On Thu, 1 May 1997, Horst von Brand wrote:
> [This message has also been posted.]
> I recently reported that .../arch/i386/kernel/init_task.c crashes
> gcc-2.7.2.2.f.2. Further investigation uncovered a subtle bug tickled by
> the union init_task_union initialization, due to the fact that spinlock_t is
> defined as an empty struct in .../include/asm-i386/spinlock.h, and is
> initialized as such here. I just reported the bug to the gcc folks, see
> below and enjoy (or weep, as the case may be). I hate to put something into
> spinlock_t just to get away with this (gcc does optimize empty structs
> away). Any other thoughts?
>
> /*
> * This jewel crashes gcc's cc1...
> * The bitfield at the beginning is necesary (a plain int won't do),
> * any intervening fields don't seem to matter.
> *
> * Compile with, e.g.:
> *
> * gcc -c tst.c
> *
> * and watch the fireworks ;-0
> *
> *
> * gcc-2.7.2.2 + g77-0.5.20, no further patches
> *
> * Reading specs from /usr/lib/gcc-lib/i586-linuxlibc1/2.7.2.2.f.2/specs
> * gcc version 2.7.2.2.f.2
> *
> * Build CFLAGS for gcc where:
> *
> * -O2 -fomit-frame-pointer \
> * -malign-functions=2 -malign-jumps=2 -malign-loops=2
> *
> * Made the three stages, no differences between stage2 and stage3
> */
>
> struct {
> int i:1;
> struct { } e;
> }
> crashit = { 0, {} };
> --
> Horst von Brand vonbrand@sleipnir.valparaiso.cl
> Casilla 9G, Viņa del Mar, Chile +56 32 672616
>