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Re: RFC: Mostly kill FRAME_CHAIN_VALID, add user knob

FYI, on the unwind branch, I'm adding the below to get_prev_frame()

/* There is always a frame. If this assertion fails, suspect that
something should be calling get_selected_frame() or
get_current_frame(). */
gdb_assert (next_frame != NULL);

if (next_frame->level >= 0
/* && !backtrace_below_main */
&& inside_main_func (next_frame->pc))
/* Don't unwind past main(), always unwind the sentinel frame.
Note, this is done _before_ the frame has been marked as
previously unwound. That way if the user later decides to
allow unwinds past main(), it can just happen. */
return 0;

/* Only try to do the unwind once. */
if (next_frame->prev_p)
return next_frame->prev;
next_frame->prev_p = 1;

Should eliminate that need to flush the frame cache everytime that command is issued (should be able to merge it into current code as well).

Looking at the other checks:

/* If we're already inside the entry function for the main objfile, then it isn't valid. */
if (inside_entry_func (get_frame_pc (fi)))
return 0;

I'd better add that one as well (but, I think, after ->prev_p). Note that this and the test below do the same thing, so only one is needed. It is just that one stops things a frame later.

/* If we're inside the entry file, it isn't valid. */
/* NOTE/drow 2002-12-25: should there be a way to disable this check? it assumes a single small entry file, and the way some debug readers (e.g. dbxread) figure out which object is the entry file is somewhat hokey. */
if (inside_entry_file (frame_pc_unwind (fi)))
return 0;

Should this one be dropped? If the user specified unwind past main, then they problably want _start() included in the backtrace. It's presence also makes the other inside_entry_file() test redundant.


PS: The command/variable should be `backtrace-*above*-main', or perhaphs `backtrace-before-main' (before ~= prev).

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