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Re: GDB on FreeBSD/Alpha


You, Mark Kettenis, were spotted writing this on Tue, May 30, 2000 at 01:09:45AM +0200:
> 
>  -g     This generates stabs-in-ecoff debugging information (which is
>         embedded in an .mdebug section in ELF).  GDB's support for
>         this particular format has suffered from some bit rot, but it
>         isn't too difficult fix.  The code is also used on MIPS, so I
>         guess this would be appreciate by a some other people too.
>         Looking through the code, there are several places where
>         stabs-in-ecoff is commented on as being a (temporary) hack.

Unless I'm mistaken, gcc doesn't know anything about ecoff -- it just
outputs stabs. gas is the program which makes the decision to use
stabs-in-ecoff. Please correct me if I'm wrong. 

I'm not at all an expert on Alpha, hence the following question might
be silly, but -- is it possible for gcc/gas on FreeBSD/Alpha to generate
true stabs (i.e. .stab and .stabstr sections) instead of stabs-in-ecoff?
What would be wrong with this? 

> 	A bigger problem is that GCC 2.95.2 doesn't output the right
> 	stabs for function arguments (and perhaps for local variables
> 	under some special circumstances).  This makes debugging
> 	really painful, since function arguments will most likely have
> 	the wrong values in GDB.  The GCC bug is fixed in the
> 	development tree.

I understand that David is going to give us gcc 2.96 on FreeBSD soon.
Is the bug fixed there?

> In the long run I'd advice FreeBSD/Alpha to standardize in DWARF 2,
> since it is used on more platforms.  

I would argue against this. Wouldn't it be better for FreeBSD/Alpha
to stay with stabs, in particular to maintain uniformity with FreeBSD/i386?
I admit I have a private interest in staying with stabs too -- I have
my own pet project which is kernel debugger support for stabs in FreeBSD,
in a working shape on i386 now. I'm not too thrilled about adding DWARF2
support there as well and bloating it out of bounds; till now I thought
I'd only need to recover stabs from stabs-in-ecoff on Alpha.

What are the advantages of DWARF2 versus stabs?

-- 
Anatoly Vorobey,
mellon@pobox.com http://pobox.com/~mellon/
"Angels can fly because they take themselves lightly" - G.K.Chesterton

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