[ruby-core:103120] [Ruby master Feature#17762] A simple way to trace object allocation

Issue #17762 has been updated by mame (Yusuke Endoh).

Description updated

Thank you all for the comments.

byroot (Jean Boussier) wrote in #note-2:
> > p obj #=> #<Object:0x...> @ (file.rb):(lineno)
> 
> I'm not too sure about that one. I suppose it's fine, but I'm not always in a situation where `p` is usable. Would `Object#allocation_source` be acceptable?

I think this is also one of the reasonable options.

In fact, my original idea was `Object#allocation_site`, but @ko1 proposed the current approach (extending `Kernel#p`).
I like his approach because it is much shorter.

----------------------------------------
Feature #17762: A simple way to trace object allocation
https://bugs.ruby-lang.org/issues/17762#change-91189

* Author: mame (Yusuke Endoh)
* Status: Open
* Priority: Normal
----------------------------------------
How about having a short hand to `ObjectSpace.trace_object_allocations_start`, `ObjectSpace.allocation_sourcefile` and `ObjectSpace.allocation_sourceline`?

They are a very powerful tool for debugging and code-reading which allows us to identify an allocation site of an object.
Though they are never lightweight, they are the last resort when you try debugging code written by someone else.

However, the names are too long for me to remember and to type. Whenever I want to use them, I have to google, copy and paste the names.

## Proposal

To enable trace allocations:

```
require "objspace/trace" #=> objspace/trace is enabled
```

To show the allocation site of an object:

```
p obj #=> #<Object:0x...> @ (file.rb):(lineno)
```

## Example

```
require "objspace/trace"
require "active_support/all"

p ActiveSupport::VERSION::STRING
  #=> "6.1.3.1" @ /home/mame/work/ruby/local/lib/ruby/gems/3.1.0/gems/activesupport-6.1.3.1/lib/active_support/gem_version.rb:15
```

## Discussion

I've attached a simple patch that is originally authored by @ko1 .

* Is the message `objspace/trace is enabled` needed or not?
* To stop the trace, you need to use `ObjectSpace.trace_object_allocations_stop`. But, I guess that it is rare that we need to stop it during debugging.
* Is it too radical to redefine `Kernel#p`? I think that it is good enough for many cases. When it matters, the original APIs (`ObjectSpace.trace_object_allocations_start`, ...) can be used.

---Files--------------------------------
objspace-trace.patch (631 Bytes)


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