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Subject: Re: [Qemu-devel] gcc auto-omit-frame-pointer vs msvc longjmp
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To: Bob Breuer <breuerr@mc.net>
Cc: "gcc@gcc.gnu.org" <gcc@gcc.gnu.org>, Kai Tietz <ktietz70@googlemail.com>, qemu-devel <qemu-devel@nongnu.org>, Mark Cave-Ayland <mark.cave-ayland@siriusit.co.uk>

On 10/19/2011 02:05 PM, Bob Breuer wrote:
> Is it possible to force a
> stackframe by just adding a suitable attribute to either the setjmp
> function prototype, or the function which calls setjmp?

The only thing I can think of that'll be portable to a large number
of versions of GCC is

  {
    int n; char *p;
    asm("" : "=r"(n) : "0"(1));
    p = __builtin_alloca(n);
    asm("" : : "r"(p));
  }

The first asm prevents constant propagation of the 1 to the alloca;
the second asm prevents the alloca from being considered dead code.


r~