Issue #9725 has been updated by Nobuyoshi Nakada.

Description updated

Building the message at creation time does not reduce memory usage and CPU time at all, just makes it earlier.
And `#inspect` method of such complex class should consider it, I don't think that huge output is not human-readable.

Anyway, unexpectedly huge result of inspection often causes problems, so the uncaught exception handler shows the class and the object ID only in that case, but it needs to build the inspection string once and discards then.
It's a long-time known issue that we need smarter way for inspection.

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Feature #9725: Do not inspect NameError target object unless verbose
https://bugs.ruby-lang.org/issues/9725#change-52234

* 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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