[Patch libitm] [V2] config-based assessment of weakref capability

[Iain Sandoe <developer at sandoe-acoustics dot co dot uk>]

Hello All,

This is the last piece needed to get libitm working on Darwin.

---

It is take 2 on auto-configury for weakrefs in libitm.

It takes into account the comments made by Rainer (and follow-up) on:
http://gcc.gnu.org/ml/gcc-patches/2011-11/msg01898.html

* moves the checking functions to config/weakref.m4

* tries to make it clear that we are checking for a specific weakref  
behavior.

-=-

If it is preferred that libitm should stand alone - then it would be  
easy to cut the relevant part of weakref.m4 back into libitm/ 
acinclude.m4.

This checked to DTRT on i686-darwin9 (weak ref doesn't behave like  
ELF's) and x86-64-darwin10/XCode 3.2.5 (weak ref behaves as per ELF).

It is my understanding from some off-list discussion reported with the  
ld64 engineer -
- that Darwin >= 10 should, in principle, support ELF-style weak refs  
(as well as the two-level and flat_namespace versions).

comments/OK for trunk?
Iain

config:

	* weakref.m4: New file.

libitm:

	* configure.ac: Use GCC_CHECK_ELF_STYLE_WEAKREF.
	* alloc_cpp.cc: Generate dummy functions if we don't
	HAVE_ELF_STYLE_WEAKREF.
	* eh_cpp.cc: Likewise.
	* configure: Regenerate.
	* aclocal.m4:  Likewise.
	* config.h.in: Likewise.

Attachment: 181573-weakref-config.txt
Description: Text document