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Re: [debug-early] C++ clones and limbo DIEs


On 02/10/2015 02:52 AM, Richard Biener wrote:
On Fri, Feb 6, 2015 at 5:42 PM, Aldy Hernandez <aldyh@redhat.com> wrote:

Of course I wonder why you need to separate handling of functions and variables

The variables need to be handled earlier, else the call to analyze_functions() will remove some optimized global variables away, and we'll never see them. I believe that Jason said they were needed up-thread.

variables.  What breaks if you emit debug info for functions before
the first analyze_functions () call?
>
> I also wonder why you restrict it to functions with a GIMPLE body.

The functions, on the other hand, need to be handled after the second call to analyze_function (and with a GIMPLE body) else we get far more function DIEs than mainline currently does, especially wrt C++ clones. Otherwise, we get DIEs for base constructors, complete constructors, and what-have-yous. Jason wanted less DIEs, more attune to what mainline is currently doing.


I'd have expected for a TU like

void foo (int, int);
int main()
{
   return 0;
}

to be able to do

(gdb) start
(gdb) ptype foo

and get a prototype for foo?  (ok, that may be -g3 stuff)

This may need frontend support. I don't think we get any of these prototype symbols in cgraphunit, at least not in the symbol table (FOR_EACH_SYMBOL). Perhaps a call from the front-ends, similar to what we do with types with debug_hooks->type_decl(). But... do really want that? Is there a practical use?


Likewise for

struct foo { int i; };
int main ()
{
   return 0;
}

This is already working if compiled with -fno-eliminate-unused-debug-types, probably by virtue of types being called from the front-ends with debug_hooks->type_decl(). We could certainly enable -fno-eliminate-unused-debug-{symbols,types} for -g3 if desirable.

Thanks for doing all this work!

Thanks for volunteering to do the LTO bits ;-).

Aldy


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