David Daney wrote:
> Curtis Taylor wrote:
> > I have a case of g++ generating this instruction:
> > add $0xe,%esp
> > and creating a non 32bit aligned %esp. This is enabling a SIGSEGV in a
> > signal handler that expects the stack to be word aligned.
> >
> > How can I find out if GCC V3.4.6 is intended to keep the stack word
> > aligned at all times as required according to System V i386 ABI v4?
> >
>
> Does the ABI really require that the stack be aligned in places other
> than at function entry?
The phrase below "At all times" has lead me to believe it's intended to
clarify that %esp should always be word aligned.
>From page 3-10 of the March 19,1997 Delta 44.6 version 4:
The stack is word aligned. Although the architecture does not
require any alignment of the stack, software convention and the
operating system requires that the stack be aligned on a word
boundary.
>From page 3-11:
Some registers have assigned roles in the standard calling
sequence:
%esp The stack pointer holds the limit of the current stack
frame, which is the address of the stack's bottom-most,
valid word. At all times, the stack pointer should point
to a word-aligned area.
=- Curtis Taylor
