Re: Missing debug information for decls in empty blocks

[Nicolas Setton <setton at act-europe dot fr>]

Hello,

> > In the context of examining the state of debug information generation with GCC
> > 3.4 and GCC 3.5, we found that nothing is generated for "foo" and "my_struct"
> > in a construct like:
> 
> I'd call it a bug.
> 
> We have new options -fno-eliminate-unused-debug-types and 
> -fno-eliminate-unused-debug-symbols.  The default is to not emit 
> type/symbol info for unused types and symbols, and these options can be 
> used to turn this off.  However, this makes no difference for this 
> testcase with gcc-3.5.  I would expect to get debug info with the 
> options, and without the options, it may or may not be there.
> 
> Using dwarf2 debug output, I get no info for the type my_struct and the 
> symbol foo.  Using stabs debug output, I get no info for the symbol foo, 
> but I do get info for the type my_struct.

Thanks for looking into this.

My understanding of the problem is that "reemit_insn_block_notes" (in
cfglayout.c) has the unwanted effect to remove blocks that contain no
instructions.

This is due to the fact that, internally, reemit_insn_block_notes only
emits BLOCK_BEG and BLOCK_END notes only for blocks that contain active
instructions.

I have written a tentative solution that fixes the problem by emitting
those notes not only for active instructions, but also for line number
notes.

I am ready to submit a patch if it is useful, or to follow instructions
on a more proper way to fix this.

Nico