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Re: Unwinding CFI gcc practice of assumed `same value' regs
Andrew Haley wrote:
Null-terminating the call stack is too well-established practice to be
changed now.
Which does not mean that the mistake should hold people back. This is
just one of the mistakes in the x86-64 ABI. It was copied from x86 and
it was wrong there already.
In practice, %ebp either points to a call frame -- not necessarily the
most recent one -- or is null. I don't think that having an optional
frame pointer mees you can use %ebp for anything random at all,
Of course it means that.
The right way to fix the ABI is to specify that %ebp mustn't be
[mis]used in this way, not to add a bunch more unwinder data.
Nope. The right way is to specify things like backtraces with the
adequate mechanism. I fully support adding the Dwarf3 unwinder
requirements.
--
â Ulrich Drepper â Red Hat, Inc. â 444 Castro St â Mountain View, CA â