Questions about using `assert` in Java

[Andrew Luo]

This makes me wonder if it is worth introducing a compiler flag that would omit assert statements from the compiled bytecode for this scenario.  Forgive me if this has been discussed and decided before though…

Thanks,

-Andrew

From: core-libs-dev <core-libs-dev-retn at openjdk.org> On Behalf Of Alan Bateman
Sent: Monday, July 17, 2023 2:08 AM
To: Daohan Qu <quadhier at outlook.com>; core-libs-dev at openjdk.org
Subject: Re: Questions about using `assert` in Java

On 15/07/2023 17:53, Daohan Qu wrote:

:

Although the assert​ keyword has been around for a long time and
is handy for invariant checks, it does not seem to be widely used.
For example, in the famous j.u.c​ packages, nearly all assert​
statements are commented out [1].

My questions are, should assert​ be heavily used in Java programs,
especially in production code? And should we enable them in the
production code?

Asserts are very useful during development or when testing, e.g. the JDK tests run with -esa and can periodically help catch issues when testing a change.

You will find places in the JDK code, esp. in performance critical code, where assertions are commented out. The reason is that asserts, even if disabled, increase the method size and can impact inlining by the compiler at run-time.  So while useful when debugging some issue in such code, they are commended out to avoid increasing the method size.

-Alan
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