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Currently the version of ASM bundled in Clojure is pretty old (circa 2005).  There are some documented performance improvements in newer versions of ASM that should speed up some things in Clojure. We would like to move to the latest stable version of ASM (4.1); the current Clojure code uses 3.3.1.  

Release notes for ASM 4.0 and 4.1.

It may not be the desired approach, but CLJ-713 has a patch related to this.

Open Questions to Resolve

Some open questions:

  1. Should we use ASM jar as is (make the dependency public) or use re-rooted versions that cannot conflict?
    1. Scala: 2.10%2B uses ASM 4.1, subsetted, and rerooted to
    2. Groovy: 2.1 (latest stable) uses ASM 4.0 external, 2.2 (next) uses ASM 4.1 external
    3. JRuby: 1.7.4 (latest stable) uses ASM 4.0, subsetted, and rerooted to According to Charles Nutter 1.7.x will stay on 4.0. As of Feb. 19, 2014 the version on master has been bumped to 4.2 as 5.0 is currently in beta.
    4. Recommend:  re-root to avoid conflicts
  2. What (if anything) needs to be done with computing stack frames to satisfy bytecode verification changes in JDK 7?
    1. Recommend: 
  3. If re-rooted, should we subset the jar and only include what we use rather than the whole jar?
    1. Recommend: yes, as long as we're modifying we might as well subset
  4. If using a re-rooted jar, should we provide a split version of the re-rooted asm to allow it to be optional for environments that don't need it?
    1. Recommend:


Next Steps

Future Steps

  1. Feb 27, 2011

    One thing to keep in mind is that from a software distributor/System administrator's point of view, bundling of libraries is generally not desirable.  Primarily this is because It makes it hard to isolate and remedy security problems.

    As a matter of fact, both Fedora and Debian strip out the ASM library and use an external dependency.  In fact, I believe both of these already use version 3 of ASM within their distributions, if I understand things correctly.

    Just something to keep in mind.


  2. Oct 11, 2012

    What would be the point of having a re-rooted asm jar that gets distributed with clojure? Why not just use the plain asm jar?

    I have done some tests and it seems a fairly minimal change to move to the latest ASM (re-rooted or not). The only change is there's a reify that needs to be changed to a proxy since ASM moved from interfaces to abstract classes. In the case of a non-rooted asm dep, the pom.xml and build.xml need to change to pass along the maven.compile.classpath property to the compile-tests task.