proposal: make -fomit-frame-pointer the default

[Michael Matz]

Hi,

On Fri, 14 Apr 2000, Thomas R. Truscott wrote:

> The -fomit-frame-pointer option saves time and space,
> and I think it should be on by default.

Then include it in your compile line.

> For a given pc/sp the debugger can determine the current function.

Correct.

> It can "search" from the beginning of the current function
> for an execution path to the given pc.
> This path will indicate any adjustments made to the sp.
> From the adjustments and the given sp it can determine the (virtual)
> frame pointer.  Given the complexity of modern debuggers,
> this sort of thing would be relatively trivial.
> Am I missing something?

May be the nontriviality of the task? You would have to build an
instruction interpreter for each target processor. A task in itself, but
not the hard one. Consider (in pseudo code):

  push this
  if a==1, jump 1
  push that
1: do sth useful
  if a!=1, jump 2
  pop that
2: pop this

I would be very interested in an algorithm, that correctly and trivially
calculates the adjustment to SP on label 1 ;)


Ciao,
Michael.