r228107 - Generalize r228066 to give all implicit global allocation functions default visibility.

[John McCall]

> On Feb 3, 2015, at 6:34 PM, Larisse Voufo <lvoufo at google.com> wrote:
> Author: lvoufo
> Date: Tue Feb  3 20:34:32 2015
> New Revision: 228107
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=228107&view=rev
> Log:
> Generalize r228066 to give all implicit global allocation functions default visibility.

This seems generally correct, but I’m suspicious about applying it to the implicit C++14 compatibility definitions.  Linkers are not generally going to give this sensible behavior: the static linker will prefer the first definition on the link line, and the dynamic linker will prefer a definition in the executable over one in the standard library.  So even if there’s a usefully optimized implementation of sized deallocation in the program, it’ll probably get clobbered by one of these useless ones.

I don’t think there’s really a fix for that except to actually trust declarations from the standard library if they exist.  (Assuming we don’t have lying library headers out there, which we might.)  And if they don’t exist, it’s fine to emit these compatibility definitions, but we shouldn’t pretend that giving them default visibility is useful; all it does it create unnecessary and probably unwanted work at load-time to dynamically merge symbols.

John.