On Fri, Nov 21, 2008 at 07:46:43PM +0100, Geert Uytterhoeven wrote:
> > up with a couple of options:
> >
> > 1) Enhance the _builtin_trap() function so that we can specify the
> > break code that is emitted. This would allow us to do something
> > like:
> >
> > static inline void __attribute__((noreturn)) BUG()
> > {
> > __builtin_trap(0x200);
> > }
I had suggested this one before ...
> > 2) Create a new builtin '__builtin_noreturn()' that expands to nothing
> > but has no CFG edges leaving it, which would allow:
> >
> > static inline void __attribute__((noreturn)) BUG()
> > {
> > __asm__ __volatile__("break %0" : : "i" (0x200));
> > __builtin_noreturn();
> > }
>
> Now I remember, yes, __builtin_trap() is how we fixed it on m68k:
I like this interface.
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=e8006b060f3982a969c5170aa869628d54dd30d8
>
> Of course, if you need a different trap code than the default, you're in
> trouble.
MIPS ISA newer than MIPS I also have conditional break codes allowing
something like this:
#define BUG_ON(condition) \
do { \
__asm__ __volatile__("tne $0, %0, %1" \
: : "r" (condition), "i" (BRK_BUG)); \
} while (0)
that is test of condition and the trap as a single instruction. Note there
are break and trap instructions on MIPS and they are basically doing the
same job ...
Ralf
