dblaikie added a comment.

In D70524#1772961 <https://reviews.llvm.org/D70524#1772961>, @probinson wrote:

> > Perhaps we should implement this mode under -fno-standalone-debug (or 
> > something more aggressive) since "standalone" is one of the only places I 
> > can think of where having the full class definition would be handy
>
> You'd also want it for type units, so they deduplicate more reliably?  And 
> probably should be DWARF only, not CodeView?  But yeah, I'm down for it.


It'd basically remove the need for type units entirely (& the DWARF would end 
up looking quite similar to DWARF using type units, just without the type units 
(well, you'd move the member variables from the type DIE In the type unit to 
the "skeleton" type DIE in the CU - but the member function handling looks very 
similar (because the skeleton type DIE ends up needing all the declarations of 
member functions in defined in the CU anyway - so the out of line definitions 
can refer to the member function declarations, their parameters, etc (since you 
can't refer to specific DIEs other than the total type DIE in a type unit)))).

Yeah, only for DWARF/I have no idea what CodeView can/would do.

> This tactic would depend on the debuggers knowing they are unlikely to get a 
> full class description and shouldn't throw away any class they've "already 
> seen."  I remember that was an issue with, uh, one of those other debuggers 
> that I never use.  They might take the first one they see, and shrug off any 
> others as not contributing anything really important.  That would have to 
> change.

My understanding with GDB is that it tends to treat the types in independent 
CUs as being potentially independent - you can violate the ODR and see that 
reflected in the type descriptions depending on where you print the type from 
(eg: print the type while you're debugging one function in one TU and you get 
that TU's view of the type, then step into a function in another TU and print 
the type and you get that TU's view of the type).

Yeah, it's not high on my list & starting with the DWARF consumers would be the 
right place.


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https://reviews.llvm.org/D70524



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