atomic-fix

Fixes arc2’s atomic macro to work in the presence of exceptions.

arc2 has a bug where calls to atomic will stop being atomic after an exception is thrown inside of a call to atomic. For example, after:

(errsafe (atomic (/ 1 0)))

further calls to atomic will no longer be atomic. This patch fixes the bug.

Get This Hack

• diff against arc2
• repository on GitHub
• download a tarball of arc2 with this patch applied

Apply This Hack to Your Arc

By using git or patch, you can incorporate this patch into your version of Arc.

With git

 $ git pull git://github.com/CatDancer/arc.git tag arc2.atomic-fix0

For example,

 $ mkdir arc
 $ cd arc
 $ git init
 $ git pull git://github.com/CatDancer/arc.git tag arc2.atomic-fix0

With patch

To apply this patch to your copy of arc using the patch command, download arc2.atomic-fix0.patch into your Arc directory, and at the Unix command line inside the Arc directory, type:

 patch <arc2.atomic-fix0.patch

“patch” is a standard utility that comes with Unix. (If you’re running Windows, iirc patch comes with cygwin).

For example,

 $ wget http://ycombinator.com/arc/arc2.tar
 [... downloading ...]
 $ tar xf arc2.tar
 $ cd arc2
 $ patch <arc2.atomic-fix0.patch
 patching [...]
 $

License

The original Arc source is copyrighted by Paul Graham and Robert Morris and licensed under the Perl Foundations's Artistic License 2.0 as described in the “copyright” file in the Arc distribution.

My changes to Arc (this patch that I wrote) are in the public domain.

The combination of the original Arc and my changes together (what you get after you apply my patch) is also licensed under the Perl Foundations's Artistic License 2.0.