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Re: Debug info for comdat functions


On Wed, Apr 18, 2012 at 03:23:35PM +0200, Jakub Jelinek wrote:
> > DW_TAG_GNU_call_site wants to refer to the called function's DIE, so
> > the function die in the separate unit needs to have its own symbol.
> > Perhaps _call_site could refer to the function symbol instead?  That
> > seems more correct anyway, since with COMDAT functions you might end
> > up calling a different version of the function that has a different
> > DIE.
> 
> At this point it is too late to change the specification of the extension.
> But you could just put in a DW_TAG_subprogram DW_AT_external declaration
> in the main .debug_info and just refer to that from call_site as well
> as from DW_AT_specification in the comdat .debug_info.  That
> DW_AT_abstract_origin is meant there to be just one of the possible many
> DIEs referring to the callee, the debug info consumer is supposed to find
> out the actual DIE that contains the code from it using its usual
> mechanisms.

That could be easily done by keeping around the original die_node of the
DW_TAG_subprogram for comdat in the main CU, create a new die_node in the
comdat unit and move all (or all but formal_parameter?) children to it
and copy/move attributes.  Thus all references to the subprogram would go
to the main .debug_info.

	Jakub


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