Re: [B2-devel] More SheepShaver segfaults on modern Ubuntu

[Dave V. <va...@us...>]

On Sun, Mar 3, 2013 at 11:40 AM, Dave Vasilevsky
<va...@us...> wrote:
> So maybe it has something to do with newer versions of GCC?

My hunch was right! Compiling with GCC 4.5 and earlier works, but with
GCC 4.6 and later does not. I did some bisecting, and relevant
difference looks like it's in ppc-dyngen-ops.cpp's op_jump_next_A0().
For the last part of that function, GCC 4.5 generates:

	cmpq	(%rax), %rdx
	jne	.L756
.L755:
	jmp	*112(%rax)
.L756:
	.p2align 4,,7
	ret
	.cfi_endproc

While GCC 4.6 generates:

	cmpq	(%rax), %rdx
	je	.L755
.L756:
	ret
.L755:
	.p2align 4,,8
	jmp	*112(%rax)
	.cfi_endproc

It looks like this should have identical effects, but it apparently
makes a difference. Any ideas what's going on?

-Dave