Feature #20429: Emit a performance warning when specially optimized core methods are redefined

• Status: Closed
• Assignee: -
• Target version: -

[byroot (Jean Boussier)]

MRI has a number of core methods with special handling in the interpreter and both JITs that if they are redefined negatively impact Ruby performance.

The methods currently are (I may be missing a few):

• Integer: #+, #-, #*, #/, #%, #<, #>, #<=, #>=
• Float: #+, #-, #*, #/, #<, #>, #<=, #>=
• String: #freeze, #size, #length, #empty?, #+, #succ, #%, #-@
• Array: #size, #length, #empty?, #hash
• Hash: #size, #length, #empty?, #[], #[]=

Noticing that a dependency do redefine one of these methods can be non-trivial, so I'd like to emit a :performance warning when it happens.

I can't really think of much reasons to redefine these aside from fun hacks, so I believe discouraging it would be valuable.

Patch: https://github.com/ruby/ruby/pull/10532

[byroot (Jean Boussier)]

• Description updated (diff)

[Eregon (Benoit Daloze)]

+1, great idea.
I will likely do the same in TruffleRuby (there is already a way to find out via --engine.TraceAssumptions but that's more general and less user-friendly).

[byroot (Jean Boussier)]

• Description updated (diff)

[matz (Yukihiro Matsumoto)]

Sounds reasonable. Accepted.

Matz.

[ko1 (Koichi Sasada)]

• Status changed from Open to Closed