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.
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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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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 <[email protected]> Reviewed-By: Rich Trott <[email protected]> Reviewed-By: Mohammed Keyvanzadeh <[email protected]> Reviewed-By: Tobias Nießen <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Darshan Sen <[email protected]>
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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 <[email protected]> Reviewed-By: Rich Trott <[email protected]> Reviewed-By: Mohammed Keyvanzadeh <[email protected]> Reviewed-By: Tobias Nießen <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Darshan Sen <[email protected]>
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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 <[email protected]> Reviewed-By: Rich Trott <[email protected]> Reviewed-By: Mohammed Keyvanzadeh <[email protected]> Reviewed-By: Tobias Nießen <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Darshan Sen <[email protected]>
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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 <[email protected]> Reviewed-By: Rich Trott <[email protected]> Reviewed-By: Mohammed Keyvanzadeh <[email protected]> Reviewed-By: Tobias Nießen <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Darshan Sen <[email protected]>
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 <[email protected]> Reviewed-By: Rich Trott <[email protected]> Reviewed-By: Mohammed Keyvanzadeh <[email protected]> Reviewed-By: Tobias Nießen <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Darshan Sen <[email protected]>
guangwong
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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/node#42749 Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Rich Trott <[email protected]> Reviewed-By: Mohammed Keyvanzadeh <[email protected]> Reviewed-By: Tobias Nießen <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Darshan Sen <[email protected]>
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decrementing an iterator returned by
std::vector::erasemay haveundefined behaviour and should not be used. Decrementing
end()on an empty container is undefined and
.erase()could leavethe container empty.
Instead, by calling
vec.erase(it--)we decrement the valid iteratorbefore the erase operation but after being passed to the erase method.
In case of
AsyncHooks::RemoveContextperform the cleanup of emptycontexts upfront using
std::remove_ifbecause the iteration getsinterrupted as soon as the context to be removed has been found.