Re: [PATCH] in_prologue() fix

[Elena Zannoni <ezannoni at cygnus dot com>]

Jim Blandy writes:
 > 
 > > It may be that the real fix is to make ecs->stop_func_start be the
 > > beginning of the function where the adjusted stop_pc is. However that
 > > would require several changes to H.I.E. But in any event in_prologue()
 > > is wrong for this particular case.
 > 
 > My first question is, if HIE can find enough symbolic information to
 > set ecs->stop_func_{name,start,end}, how come in_prologue can't find
 > it?
 > 

I am not sure I understand your question.  in_prologue finds the start
and end of the function within which pc is (in the same way HIE does for
the wrong pc). Because of the way in_prologue works, the info found is
not compared with the input function address. Doing this would be
another way to fix the problem, but you would have to rewrite
in_prologue. What I am trying to say is that in_prologue takes 2
inputs: a pc and a function start address. It has to determine if the
pc is within the prologue of the function starting at the address. In
this case it gets it wrong because it doesn't think about checking if pc
is within the function at all. 


 > In other words: your explanation implies that HIE has some way to find
 > the function extent, but happens to be wrong because of
 > DECR_PC_AFTER_BREAK lossage.  But in_prologue knows the correct PC;
 > why can't it use the same mechanism HIE used earlier to get the right
 > answer?
 > 

It does use the same mechanism (find_pc_partial_function) but it
doesn't check the results properly.

 > Also, aren't there other adverse consequences when
 > ecs->stop_func_{name,start,end} are wrong?  I think the HIE fix is the
 > right thing.  HIE is painful for me too, but otherwise, you'll just
 > get another CR in a month.
 > 

So I thought too. But in case of breakpoint being hit,
bpstat_stop_status() computes the stop_pc again, and corrects it. All
the info is printed correctly. I haven't looked at this in too much
detail though. I can add a FIXME to HIE to warn for the possibility of 
problems down the road. I have no time now to try to fix this.

 > If you've tested the change on SPARC and i386, it's okay with me.

I tested on sparc, I will test on linux.

Elena