Re: GDB scope does not work quite right for Pascal

levi
2002-02-01T12:29:37Z

At 14:18 12/10/01 -0400, Oldham, Adam wrote:
>Yes, I saw some of these threads, but nothing seemed to shed light on fixes
>for the scoping of this. It is good to know Ada does this as well so that
>maybe us Ada/Pascal people can get together and come up with a fix.
>
>I submitted code that demonstrates this with my bug report as well....

After some testing on both GNU C and GNU Pascal
I discovered that they both use the same method (on djgpp i386 target)

The calling frame pointer is passed to the nested function
in %ecx register and stored in -4(%ebp) in the function prologue
(which does not seem to be handled by skip_prologue function,
at least I didn't find anything in version 5.0 sources)

So the parent frame is placed in %ecx and
stored at offset -4 for GNU gcc or gpc
while it is pushed at offset 8 in Free Pascal code.

Using -gstabs+ I saw nothing generated to explain the meaning
of the %ecx parameter or the -4(%ebp) location.

Checking the prologue for this movl %ecx,offset(%ebp)
isn't probably sufficient to tell that we are in a nested proc...
Moreover this is processor specific, which is bad...

Stabs does give info about nesting in the stabs concerning the

Consider the following source:
int
test ()
{
int i = 1;
int j;

int local ()
{
return j+1;
};

j = i+1;
return local ();
}

int
main ()
{
printf(" result of test() is %d \n",test());
return 0;
}

This generates
.stabs "local:f(0,1),local,test",36,0,8,_local.3
The ,local,test indicates that local is nested inside test function.

But this is not enough as I don't know what happens for instance
if parameters are passed by registers...

Adding some debug info concerning the location of the
parent frame seems like a good idea, no ?
The Free Pascal approach to use a pseudo parameter called
'parent_ebp' seems to not be applicable to C as this would
be a valid C local variable name. Maybe something beginning
with a dollar like for the classes?

A similar problem exists for With statements in pascal.
Stabs defines even a specific stab number for this but this
is also unsupported for now.