frameless functions

frameless functions

[Jan Hoogerbrugge]

Hi,

I porting gdb to a new target. The port is now in a stage where stack traces 
seem to work when code is compiled with a frame pointer. Now I am trying to 
get it working for code without a frame pointer. Could anyone tell me how to 
deal with frameless functions? Is there another port where I can learn from?

My compiler assigns the incoming sp to the fp. I guess this is what most 
compilers do.

In scan_prologue() I use fi->frame, which appears to correspond to the fp, 
to determine where registers are saved. What to do in the case of frameless 
functions? Should I assign something to fi->frame?

Should I define frameless_function_invocation()?

Thanks in advance,
Jan





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Re: frameless functions

[Andrew Cagney]

> Hi,
> 
> I porting gdb to a new target. The port is now in a stage where stack traces seem to work when code is compiled with a frame pointer. Now I am trying to get it working for code without a frame pointer. Could anyone tell me how to deal with frameless functions? Is there another port where I can learn from?
> 
> My compiler assigns the incoming sp to the fp. I guess this is what most compilers do.
> 
> In scan_prologue() I use fi->frame, which appears to correspond to the fp, to determine where registers are saved. What to do in the case of frameless functions? Should I assign something to fi->frame?
> 
> Should I define frameless_function_invocation()?

I'd ignore that method, it doesn't do much useful.  You'll need to do at 
least a minimal prologue analysis to determine the address of the 
frameless frames `base'.  You need to do this anyway to determine where 
any pushed registers are.

As an alternative, your architecure might have debug info that lets you 
locate the frame base.

I should also note that the frame code is being rewritten so when it 
comes to integrate your architecture into GDB, you're going to encounter 
some radical change.

Andrew