[v3] libstdc++/20534, debug mode vs. includes

[Paolo Carlini]

Paolo Carlini wrote:

>Benjamin, can I ask you a courtesy? Before committing this patch, can
>you double check that the use of <debug/string> is still ok? Quickly
>looking at the code I'm not 100% sure: had this paranoic doubt this
>morning when waking up. Maybe <string/debug> should set on its own
>_GLIBCXX_DEBUG before including <string>?!? I don't think we are asking
>the user to pass -D_GLIBCXX_DEBUG even when using <debug/string> directly.
>  
>
Ok, just checked: everything is ok. Sorry for the false alarm!

Paolo.