r188739 - Revert "Revert "Revert "Revert "DebugInfo: Omit debug info for dynamic classes in TUs that do not have the vtable for that class""""

[Adrian Prantl]

On Dec 16, 2013, at 4:54 PM, Greg Clayton <gclayton at apple.com> wrote:

> 
> On Dec 16, 2013, at 2:55 PM, David Blaikie <dblaikie at gmail.com> wrote:
> 
>> 
>> 
>> 
>> On Mon, Dec 16, 2013 at 2:44 PM, Adrian Prantl <aprantl at apple.com> wrote:
>> Hi Chandler and David,
>> 
>> unfortunately it looks more like case 1. This optimization breaks several assumptions that tools in our software stack depend on.
>> 
>> It's a fairly substantial debug info size savings that seems worth investigating whether you can keep it enabled at least in 
>> 
>> - For example, it breaks dtrace, which on Darwin relies on being able to pull the (complete) CTF info (compact C type format) out of the DWARF in the .dSYM for a given module.
>> 
>> I take it you're already using -fno-limit-debug-info for these scenarios, then? (are you using -flimit-debug-info at all?)
> 
> Yes, this is what will need to happen now that clang has changed.

In case this wasn't clear enough: Currently, this optimization is totally orthogonal to limited debug info. Passing -fno-limit-debug-info will not make any of these examples work. This thread is about adding an additional flag to the frontend that controls this optimization.

I guess we could make also it part of -flimit-debug-info, either way will work.

-- adrian