Some static initialisers still run at compile time if used in type hints

Description

AOT compiling on an x86 machine to be run on an ARM machine when a Java dependency has a native component and the class with the native dependency is used in a type hint.

In this situation, the only native library available on the classpath is the ARM dependency, and obviously won't load on the compiling x86 machine. Java libraries tend to load the native dependencies in the static initialiser of the class, which will fail in this situation as the architecture is x86 and the dependencies are ARM, for which reason made the change to not run static initialisers at compile time.

This covers a case which didn't come up as part of CLJ-1315, that the same problem occurs if rather than constructing the class, you simply use it as a type hint (which IMO is doubly surprising as something to have a side-effect).

Approach: Don't cause class to load merely from being in a type hint.

Patch: clj-1714-4.patch

This patch has been used in production for over a year with no adverse effects (as has anybody using the clojure-android build of clojure).

Prescreened: Alex Miller

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AdamClements
July 31, 2015, 4:56 PM

Example problem:
AOT compiling on an x86 machine to be run on an ARM machine when a Java dependency has a native component and the class with the native dependency is used in a type hint.

In this situation, the only native library available on the classpath is the ARM dependency, and obviously won't load on the compiling x86 machine. Java libraries tend to load the native dependencies in the static initialiser of the class, which will fail in this situation as the architecture is x86 and the dependencies are ARM, for which reason made the change to not run static initialisers at compile time.

This covers a case which didn't come up as part of CLJ-1315, that the same problem occurs if rather than constructing the class, you simply use it as a type hint (which IMO is doubly surprising as something to have a side-effect).

This patch fixes that - happy to try and create a test, but would appreciate some advice on the shape such a test would take - presumably loading a java native library would be undesirable. I could simply check for static initialisers being run, but first would need some agreement that this is universally undesirable at compile time.

I have been using this patch in production for over a year with no adverse effects (as has anybody using the clojure-android build of clojure).

Stuart Halloway
July 31, 2015, 5:34 PM

Hi Adam,

Thanks for the quick response. I think checking for static initializers being run is OK for a test.

AdamClements
August 12, 2015, 3:12 PM

Added failing tests which now pass

Michael Blume
September 28, 2016, 8:07 PM

Updated patch to apply to master

Alex Miller
September 28, 2016, 8:40 PM

Added new patch that is semantically identical, just easier to read (with formatted using -U8). Attribution retained.

Completed

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Reporter

AdamClements

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