async_hooks: avoid decrementing iterator after erase - #42749
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decrementing an iterator returned by `std::vector::erase` may have undefined behaviour and should not be used. Decrementing `end()` on an empty container is undefined and `.erase()` could leave the container empty. Instead, by calling `vec.erase(it--)` we decrement the valid iterator before the erase operation but after being passed to the erase method. In case of `AsyncHooks::RemoveContext` perform the cleanup of empty contexts upfront using `std::remove_if` because the iteration gets interrupted as soon as the context to be removed has been found.
addaleax
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Trott
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I imagine there's no easy way to add a test for this, but mentioning it anyway in case I'm wrong.
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I also don't think that would be easy to write since it is difficult to test undefined behaviour. It might even act differently on different stl implementations (on some even work correctly). But the new approach should not be controversial and existing tests must stay all green. |
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xtx1130
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decrementing an iterator returned by `std::vector::erase` may have undefined behaviour and should not be used. Decrementing `end()` on an empty container is undefined and `.erase()` could leave the container empty. Instead, by calling `vec.erase(it--)` we decrement the valid iterator before the erase operation but after being passed to the erase method. In case of `AsyncHooks::RemoveContext` perform the cleanup of empty contexts upfront using `std::remove_if` because the iteration gets interrupted as soon as the context to be removed has been found. PR-URL: nodejs#42749 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Rich Trott <rtrott@gmail.com> Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Darshan Sen <raisinten@gmail.com>
targos
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decrementing an iterator returned by `std::vector::erase` may have undefined behaviour and should not be used. Decrementing `end()` on an empty container is undefined and `.erase()` could leave the container empty. Instead, by calling `vec.erase(it--)` we decrement the valid iterator before the erase operation but after being passed to the erase method. In case of `AsyncHooks::RemoveContext` perform the cleanup of empty contexts upfront using `std::remove_if` because the iteration gets interrupted as soon as the context to be removed has been found. PR-URL: #42749 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Rich Trott <rtrott@gmail.com> Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Darshan Sen <raisinten@gmail.com>
juanarbol
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decrementing an iterator returned by `std::vector::erase` may have undefined behaviour and should not be used. Decrementing `end()` on an empty container is undefined and `.erase()` could leave the container empty. Instead, by calling `vec.erase(it--)` we decrement the valid iterator before the erase operation but after being passed to the erase method. In case of `AsyncHooks::RemoveContext` perform the cleanup of empty contexts upfront using `std::remove_if` because the iteration gets interrupted as soon as the context to be removed has been found. PR-URL: #42749 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Rich Trott <rtrott@gmail.com> Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Darshan Sen <raisinten@gmail.com>
danielleadams
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Jun 27, 2022
decrementing an iterator returned by `std::vector::erase` may have undefined behaviour and should not be used. Decrementing `end()` on an empty container is undefined and `.erase()` could leave the container empty. Instead, by calling `vec.erase(it--)` we decrement the valid iterator before the erase operation but after being passed to the erase method. In case of `AsyncHooks::RemoveContext` perform the cleanup of empty contexts upfront using `std::remove_if` because the iteration gets interrupted as soon as the context to be removed has been found. PR-URL: #42749 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Rich Trott <rtrott@gmail.com> Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Darshan Sen <raisinten@gmail.com>
targos
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Jul 11, 2022
decrementing an iterator returned by `std::vector::erase` may have undefined behaviour and should not be used. Decrementing `end()` on an empty container is undefined and `.erase()` could leave the container empty. Instead, by calling `vec.erase(it--)` we decrement the valid iterator before the erase operation but after being passed to the erase method. In case of `AsyncHooks::RemoveContext` perform the cleanup of empty contexts upfront using `std::remove_if` because the iteration gets interrupted as soon as the context to be removed has been found. PR-URL: #42749 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Rich Trott <rtrott@gmail.com> Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Darshan Sen <raisinten@gmail.com>
guangwong
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Oct 10, 2022
decrementing an iterator returned by `std::vector::erase` may have undefined behaviour and should not be used. Decrementing `end()` on an empty container is undefined and `.erase()` could leave the container empty. Instead, by calling `vec.erase(it--)` we decrement the valid iterator before the erase operation but after being passed to the erase method. In case of `AsyncHooks::RemoveContext` perform the cleanup of empty contexts upfront using `std::remove_if` because the iteration gets interrupted as soon as the context to be removed has been found. PR-URL: nodejs/node#42749 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Rich Trott <rtrott@gmail.com> Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Darshan Sen <raisinten@gmail.com>
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decrementing an iterator returned by std::vector::erase may have
undefined behaviour and should not be used. Decrementing end()
on an empty container is undefined and .erase() could leave
the container empty.
Instead, by calling vec.erase(it--) we decrement the valid iterator
before the erase operation but after being passed to the erase method.
In case of AsyncHooks::RemoveContext perform the cleanup of empty
contexts upfront using std::remove_if because the iteration gets
interrupted as soon as the context to be removed has been found.