http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49230
gee <jojelino at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |UNCONFIRMED
Resolution|INVALID |
--- Comment #7 from gee <jojelino at gmail dot com> 2011-06-29 19:35:20 UTC ---
(In reply to comment #3)
> As register ebp is used by gcc as internal frame-register. Even if you are
> specifying -fomit-frame-pointer as option, the main function will still have a
> frame-pointer setup. Also ebp-register is a callee-saved register, which means
> its use as local-register variable is in general nothing wise to do.
maybe the following could be counterexample.
this code is from gcc 2011110622.
ebp may be not internal frame pointer.
so in this case setjmp can store invalid ebp.
nlg_notify dereferences ebp,causing sigsegv
not only it don't use framepointer, but also it doesn't restore framepointer
LFE104:
.p2align 4,,15
.globl _rb_ensure
.def _rb_ensure; .scl 2; .type 32; .endef
_rb_ensure:
LFB105:
.loc 2 727 0 is_stmt 1
.cfi_startproc
LVL835:
pushl %ebx
LCFI228:
.cfi_def_cfa_offset 8
.cfi_offset 3, -8
subl $120, %esp
LCFI229:
.cfi_def_cfa_offset 128
LBB566:
.loc 2 731 0
movl _ruby_current_thread, %eax
LBE566:
.loc 2 729 0
movl $4, 32(%esp)
LVL836:
LBB567:
.loc 2 731 0
movl $0, 100(%esp)
movl %eax, %edx
movl %eax, 28(%esp)
LVL837:
movl 152(%eax), %eax
movl %eax, 108(%esp)
leal 36(%esp), %eax
movl %eax, 152(%edx)
.loc 2 732 0
movl %eax, (%esp)
call __setjmp
LVL838:
testl %eax, %eax
movl %eax, %ebx
LVL839:
je L733
.loc 2 735 0
movl 108(%esp), %eax
LVL840:
movl 28(%esp), %edx
movl %eax, 152(%edx)
LBE567:
.loc 2 738 0
movl 140(%esp), %eax
movl %eax, (%esp)
call *136(%esp)
LVL841:
.loc 2 740 0
movl _ruby_current_thread, %eax
movl %ebx, 4(%esp)
movl 152(%eax), %eax
movl %eax, (%esp)
call _longjmp
LVL842:
.p2align 4,,10
L733:
LBB568:
.loc 2 733 0
movl 132(%esp), %eax
movl %eax, (%esp)
call *128(%esp)
LVL843:
.loc 2 735 0
movl 28(%esp), %edx
.loc 2 733 0
movl %eax, 32(%esp)
.loc 2 735 0
movl 108(%esp), %eax
movl %eax, 152(%edx)
LBE568:
.loc 2 738 0
movl 140(%esp), %eax
movl %eax, (%esp)
call *136(%esp)
LVL844:
.loc 2 741 0
movl 32(%esp), %eax
.loc 2 742 0
addl $120, %esp
LCFI230:
.cfi_def_cfa_offset 8
popl %ebx
LCFI231:
.cfi_def_cfa_offset 4
.cfi_restore 3
LVL845:
ret
.cfi_endproc
LFE105:
.p2align 4,,15
.globl _rb_frame_this_func
.def _rb_frame_this_func; .scl 2; .type 32; .endef
_rb_frame_this_func:
LFB108:
.loc 2 791 0
.cfi_startproc
.loc 2 792 0
movl _ruby_current_thread, %eax
movl 16(%eax), %eax
jmp _frame_func_id
LVL846:
.cfi_endproc
LFE108:
