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Re: svn commit: r1298554 - in /subversion/branches/revprop-cache: build/ac-macros/svn-macros.m4 configure.ac

From: Stefan Fuhrmann <eqfox_at_web.de>
Date: Fri, 09 Mar 2012 20:20:36 +0100

On 09.03.2012 15:40, Daniel Shahaf wrote:
> stefan2_at_apache.org wrote on Thu, Mar 08, 2012 at 20:07:43 -0000:
>> Author: stefan2
>> Date: Thu Mar 8 20:07:43 2012
>> New Revision: 1298554
>>
>> URL: http://svn.apache.org/viewvc?rev=1298554&view=rev
>> Log:
>> Teach subversion to detect the availability of GCC's atomic built-ins
>> for 64 bit items. This code was taken from APR and tweaked slightly.
>>
>> * build/ac-macros/svn-macros.m4
>> (SVN_CHECK_FOR_ATOMIC_BUILTINS): new macro
>> * configure.ac
>> call the new macro, set SVN_HAS_ATOMIC_BUILTINS #define
>>
>> Modified:
>> subversion/branches/revprop-cache/build/ac-macros/svn-macros.m4
>> subversion/branches/revprop-cache/configure.ac
>>
>> Modified: subversion/branches/revprop-cache/build/ac-macros/svn-macros.m4
>> URL: http://svn.apache.org/viewvc/subversion/branches/revprop-cache/build/ac-macros/svn-macros.m4?rev=1298554&r1=1298553&r2=1298554&view=diff
>> ==============================================================================
>> --- subversion/branches/revprop-cache/build/ac-macros/svn-macros.m4 (original)
>> +++ subversion/branches/revprop-cache/build/ac-macros/svn-macros.m4 Thu Mar 8 20:07:43 2012
>> @@ -202,3 +202,44 @@ AC_DEFUN([SVN_REMOVE_STANDARD_LIB_DIRS],
>> printf "%s" "${output_flags# }"
>> fi
>> ])
>> +
>> +AC_DEFUN([SVN_CHECK_FOR_ATOMIC_BUILTINS],
>> +[
>> + AC_CACHE_CHECK([whether the compiler provides atomic builtins], [ap_cv_atomic_builtins],
> How does this interact with
> http://subversion.apache.org/docs/release-notes/1.7#rhel-2-issue
> ? (which says: "Workarounds include using a more recent gcc or
> configuring APR with --disable-nonportable-atomics.")
>
> Should the new code be disabled for old gcc's?

That bug is in APR/atomic/unix/ia32.c. The built-ins that
I check for are similar to APR/atomic/unix/builtins.c.
But I would be fine with disabling this code for older GCCs.

We need to test it on 32 bit unix anyways since the compiler
needs to create a longer instruction sequence on those
machines. Writing a thorough test for the new API will be
some non-trivial task.

-- Stefan^2.
Received on 2012-03-09 20:21:05 CET

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