On 06/26/2018 07:01 AM, Florian Weimer wrote:
On 06/26/2018 12:56 PM, Nathan Sidwell wrote:
On 06/26/2018 05:26 AM, Florian Weimer wrote:
So it looks to me that the caller of _Unwind_Find_FDE needs to ensure
that the PC is a valid element of the call stack. Is this a correct
assumption?
I thought this was an (implicit?) requirement. You're unwinding a
stack to deliver an exception up it. Are there use cases where that
is not the case?
We have something approaching this scenario.
pthread_cancel in glibc unwinds the stack using DWARF information until
encounters a frame without unwind information, when it switches to
longjmp to get past that obstacle.
This is a long jump to the originating pthread function at the end of
the stack, right? We not only get past the obstacle, but any and all
DWARF frames on top of it. (just for my understanding)
However, at the point of transition from a valid DWARF frame into the
wilderness (without unwind data), we should still have accurate
information on the caller's PC, so _Unwind_Find_FDE will reliably fail
to find any unwind data for it. It's not a random pointer somewhere
else, so I think even the pthread_cancel case is fully supported.
That sounds right. It's a PC that you could return to if you weren't
trying to unwind the stack.
nathan
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Nathan Sidwell