[ruby-core:99679] [Ruby master Feature#17103] Add a :since option to ObjectSpace.dump_all

[jean.boussier@gmail.com]

Issue #17103 has been updated by byroot (Jean Boussier).


> this feature strongly connected with trace_object_allocations, right?

Indeed.

> so please write it on document. what happens on without trace_object_allocations? it is unclear.

I changed:

```
Objects that were allocated with object allocation tracing disabled are not dumped.
```

to:

```
Objects that were allocated without object allocation tracing enabled
are ignored. See ::trace_object_allocations for more information and
examples.
```

Is that acceptable?

----------------------------------------
Feature #17103: Add a :since option to ObjectSpace.dump_all
https://bugs.ruby-lang.org/issues/17103#change-87166

* Author: byroot (Jean Boussier)
* Status: Open
* Priority: Normal
----------------------------------------
Patch: https://github.com/ruby/ruby/pull/3368

This is useful for seeing what a block of code allocated, e.g.

```ruby
GC.start
GC.disable
gc_gen = GC.count
ObjectSpace.trace_object_allocations do
  # run some code
end
allocations = ObjectSpace.dump_all(output: :file, since: gc_gen)
GC.enable
GC.start
retentions = ObjectSpace.dump_all(output: :file, since: gc_gen)
```

For context, this is what I do in https://github.com/Shopify/heap-profiler, except that I have to dump the entire heap three times and then do a diff. This new API would allow me to dump the entire heap only once and then do two much-faster single-generation dumps without doing the diff.



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