Issue #9725 has been updated by Charles Nutter.


I think we're going to have to make this change unilaterally in JRuby.

This behavior leads to unpredictable systems, since NameErrors can happen even in tested code, and you'll never know how big the attached object might be. One untested code path leading to NameError and you might blow the memory cap of the entire system.

I really hope MRI decides to fix this.

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Feature #9725: Do not inspect NameError target object unless verbose
https://bugs.ruby-lang.org/issues/9725#change-52226

* Author: Charles Nutter
* Status: Open
* Priority: Normal
* Assignee: 
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At least once every few months, we get an error report of JRuby raising a memory error where MRI does not due to NameError's Message object holding a reference to an object that's too large to inspect. I propose that this inspection of the target object should only be done in verbose mode.

Background:

NameError is raised when a variable-like method call fails to find a defined method. The resulting exception is created with a hidden NameError::Message that holds the object in which the method could not be found.

When name error needs to render its message, such as when it bubbles out or when #message is called, it does to_str on the NameError::Message, which ends up inspecting the target object. If this object's inspect output is large (or infinite) it can end up consuming a large amount of memory.

Problems:

* If the amount of memory required to render a NameError exceeds available memory, a very confusing and misleading memory error can be raised instead.
* If the target object is considered sensitive data, it will end up bubbling out through potentially untrustworthy code. It is an encapsulation flaw, basically.
* A NameError that gets held in memory will also prevent GC of the object it references.

Solutions:

* NameError should not capture the target object.
* NameError should build a message based on the target object *at creation time*, and only include information useful to indicate the type of object.
* (Optional) If verbose mode is set, NameError can just do what it does now.



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