[lldb-dev] Problem unwinding from inside of a CRT function

Zachary Turner zturner at google.com
Thu Jan 15 17:01:49 PST 2015

Btw, I'm still a little uncomfortable that not having unwind/ symbol info
at any point no matter how deep in a function call chain, has the
possibility to mess up a step over. In my original example, i had symbols
for main but not printf. Is that not sufficient to step over a call to
printf? It should be able to know from that a) the bounds of main(), b) the
pc corresponding to the next line of source after printf, and c) the value
of esp. Aren't those 3 pieces of information enough to step over any line
of source, regardless of whether you have unwind information for the code
inside the function you're stepping over?
On Thu, Jan 15, 2015 at 4:36 PM <jingham at apple.com> wrote:

> > On Jan 15, 2015, at 4:18 PM, Zachary Turner <zturner at google.com> wrote:
> >
> > Which is unfortunate, because it seems to be needed even for basic
> stepping to work, like step over.  Originally I was just trying to
> implement stepping, and that's how I ran into this issue.  So that brings
> me to a related question.  Why is step over as complicated as it is?  It
> seems to me like step over can be implemented by disassembling 1 opcode,
> adding the size of the opcode to the current pc, and having the
> ThreadPlan::ShouldStop always return false unless the pc is equal to old_pc
> + size_of_opcode.
> >
> You are describing "thread step-inst".  That should pretty much always
> work regardless of unwinder, etc.
> Source step over, as Jason said, is much more complicated.
> Jim
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