Geert Uytterhoeven wrote:
On Fri, 21 Nov 2008, Alan Cox wrote:
On Thu, 20 Nov 2008 17:26:36 -0800
David Daney <ddaney@xxxxxxxxxxxxxxxxxx> wrote:
MIPS: Make BUG() __noreturn.
Often we do things like put BUG() in the default clause of a case
statement. Since it was not declared __noreturn, this could sometimes
lead to bogus compiler warnings that variables were used
uninitialized.
There is a small problem in that we have to put a magic while(1); loop to
fool GCC into really thinking it is noreturn.
That sounds like your __noreturn macro is wrong.
Try using __attribute__ ((__noreturn__))
if that works then fix up the __noreturn definitions for the MIPS and gcc
you have.
Nope, gcc is too smart:
$ cat a.c
int f(void) __attribute__((__noreturn__));
int f(void)
{
}
$ gcc -c -Wall a.c
a.c: In function f:
a.c:6: warning: `noreturn' function does return
$
That's right.
I was discussing this issue with my colleague Adam Nemet, and we came
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);
}
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();
}
David Daney
