The locking macro fails bytecode verification on Graal native-image and ART runtime

Description

Android ART runs compile time verification on bytecode and fails on any usage of the locking macro. The error looks like that seen in CLJ-1829 (in that case clojure.core.server/stop-server calls the locking macro):

Cause: From discussion on an Android issue (https://code.google.com/p/android/issues/detail?id=80823), it seems this is due to more strictly enforcing the "structural locking" provisions in the JVM spec (https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-2.html#jvms-2.11.10).

It appears that the mixture of monitor-enter, monitor-exit, and the try/finally block in `locking` create paths that ART is flagging as not having balanced monitorenter/monitorexit bytecode. Particularly, monitorenter and monitorexit themselves can throw (on a null locking object). The Java bytecode does some tricky exception table handling to cover these cases which (afaict) is not possible to do without modifying the Clojure compiler.

Approach: One possible approach is to have locking invoke the passed body in the context of a synchronized block in Java. This avoids the issue of the tricky bytecode by handing it over to Java but has unknown performance impacts.

Patch: clj-1472-3.patch

See also: Examination of the bytecode as compared to a java synchronized block shows up a number of differences:
https://gist.github.com/AdamClements/2ae6c4919964b71eb470

Screened by: Alex Miller - I'm marking this screened as I think it is a viable approach that fixes the issue and due to the infrequency of its use, I'm not really that concerned about it being a performance problem. I will flag that I think another way to handle this would be to make `locking` a special form with compiler support, but I'm not sure whether that's worth doing or not, so I will leave that to Rich to decide.

Environment

Android ART runtime

Status

Assignee

Unassigned

Reporter

AdamClements

Labels

Approval

Vetted

Patch

Code

Affects versions

Priority

Critical
Configure