Re: [RFA] Artifical dwarf2 debug info

[Andrew Cagney <ac131313@redhat.com>]

> On Tue, Dec 17, 2002 at 09:23:15AM -0500, Andrew Cagney wrote:
> 
>> >Ehm ... what's the result regarding to my patch, guys?
> 
>> 
>> I think pending changes for the most part render the cornerstone of this 
>> patch obsolete.  This is because the dwarf2cfi code wont't be called 
>> when the frame doesn't have dwarf2 info -> the case that this code is 
>> trying to handle.
>> 
>> The idea of being able to create debug info at run time, though, is very 
>> much worth persuing.
> 
> 
> Eh, I don't agree at all.  We'll be calling a function to figure out if
> the affected PC value has CFI information.  Where's that function going
> to live?  In the CFI reader presumably, and it would be the appropriate
> time to construct fake debug info.
> 
> I think that Michal's patch would look substantively the same after
> these pending changes.

Not bits like this (michael, is this actually separate and how does it 
compare to the code identifying a frameless function?)

>  CORE_ADDR
>  x86_64_skip_prologue (CORE_ADDR pc)
>  {
> @@ -863,19 +883,8 @@ x86_64_skip_prologue (CORE_ADDR pc)
>    struct symbol *v_function;
>    CORE_ADDR endaddr;
>  
> -  /* We will handle only functions beginning with:
> -     55          pushq %rbp
> -     48 89 e5    movq %rsp,%rbp 
> -   */
> -  unsigned char prolog_expect[PROLOG_BUFSIZE] = { 0x55, 0x48, 0x89, 0xe5 },
> -    prolog_buf[PROLOG_BUFSIZE];
> -
> -  read_memory (pc, (char *) prolog_buf, PROLOG_BUFSIZE);
> -
> -  /* First check, whether pc points to pushq %rbp, movq %rsp,%rbp.  */
> -  for (i = 0; i < PROLOG_BUFSIZE; i++)
> -    if (prolog_expect[i] != prolog_buf[i])
> -      return pc;		/* ... no, it doesn't. Nothing to skip.  */
> +  if (! x86_64_function_has_prologue (pc))
> +    return pc;

And I don't think this would be used either.   Instead the decision to 
create the FDE would have been made earlier.

> @@ -839,6 +785,9 @@ frame_state_for (struct context *context
>    context->lsda = 0;
>  
>    fde = get_fde_for_addr (context->ra - 1);
> +  
> +  if (fde == NULL)
> +    fde = guess_generic_fde (context->ra - 1);
>  
>    if (fde == NULL)
>      return;

However, the code masaging would likely be the same, yes.

Andrew

(hmm, bet that context->ra - 1 should be frame_address_in_block (fi))