Re: Atomic increment/decrement

Hopefully, this e-mail will get through to the icu mailing list.  IBM 
e-mails don't seem to work with the mailing lists today.

I do not agree with this proposal.  ICU should work on older versions of 
an operating system.  We try our very best to allow ICU binaries built on 
a new version of an operating system to work on older operating systems 
too. This is mainly with regards to the core library code.  The test code 
doesn't count.

Some non-core Apple people do distribute ICU binaries to older versions of 
Mac OS X.  Open Office and several other groups would have to know about 
this versioning problem, if this feature was added.  Most people want ICU 
to work, and they don't want to know the details :-/

The default should be to use all functions that are available to all 
recent versions of Darwin, and not the ones that may be occasionally 
there.  This doesn't mean that you can't turn on this feature.  It just 
means that the default is to use the standard way of doing things.

If you want to add something like -DU_USE_MACOSX_ATOMIC_INCREMENT or 
something like that to Apple's build script to enable this in ICU, that 
would be fine to add.  Configure should not be used to detect this 
feature, since you really have to know what you're doing to use this 
feature (I believe this includes you).

So to summarize...  It's okay to add this code to ICU, but it's not okay 
to use it by default.

George Rhoten
IBM Globalization Center of Competency/ICU  San José, CA, USA



Deborah Goldsmith <[email protected]> 
Sent by: [email protected]
11/16/2004 04:11 PM

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icu list <[email protected]>
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Subject
Atomic increment/decrement






I'd like to have umutex.c take advantage of built-in atomic 
increment/decrement functions on Darwin. The Darwin-specificity can be 
taken care of by using a U_DARWIN conditional compile. The sticky issue 
is that they are not available on all versions of Darwin (just as ICU 
has new functions added each release).

On top of that, Darwin does not have a global "version of Darwin" 
preprocessor variable defined. So it looks like this will require 
adding something to configure_in to test for the presence of these 
particular functions, or ICU won't compile on a version of Darwin 
lacking these functions.

Beyond that, does there need to be a runtime test, to allow a version 
of ICU built on a version of Darwin that has the functions, to run on a 
version of Darwin that doesn't have the functions? In general ICU 
doesn't seem to go that far in terms of testing for availability: it 
only checks for what's on the system you're building on. Apple doesn't 
particularly have a need for this, either: for us it's OK for a version 
of ICU built on Darwin version A to only run on A or later.

I'd be curious to hear people's thoughts on the best way of doing this. 
I already had a private exchange with Steven about this.

Deborah

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