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> Even std::unique_ptr has runtime costs in release builds that a raw pointer does not. O RLY ? https://gcc.godbolt.org/z/QhbUjI https://gcc.godbolt.org/z/Qhb

> Even std::unique_ptr has runtime costs in release builds that a raw pointer does not. O RLY ? https://gcc.godbolt.org/z/QhbUjI https://gcc.godbolt.org/z/QhbUjI

abainbridge 7y ago
How would I create the pointer to int in the unique_ptr case without initializing the int? I tried this: https://gcc.godbolt.org/z/SfVxzU https://gcc.godbolt.org/z/SfVxzU I expect there is a way, just I don't know it.
- jcelerier 7y ago
  See the docs : https://en.cppreference.com/w/cpp/memory/unique_ptr/make_unique https://en.cppreference.com/w/cpp/memory/unique_ptr/make_uni... For C++ < 20 replace `std::make_unique<int>()` by `std::unique_ptr<int>(new int)` (which with all explicit uses of `new` can end up not being safe in some cases (in that case, only if you've not enough memory to allocate an int which should not really be a common occurence...) For C++ >= 20 you get std::make_unique_default_init which does that properly.
  - deleted 7y ago
    [deleted]
- einpoklum 7y ago
  Have created a Stackoverflow question focused on this point: https://stackoverflow.com/q/58050872/1593077 https://stackoverflow.com/q/58050872/1593077
Pombal 7y ago
Yes, really. It's fine for simple types but for more complex types in more complex situations, you pay the price. Unique pointers carry around not just the type but also a default deleter, if you provide one. That deleter has to be copied around, checked for nullptr before execution and set to nullptr when ownership changes. For even more examples of this have a look at this talk when it comes out: https://cppcon2019.sched.com/event/Sfq4/there-are-no-zero-cost-abstractions https://cppcon2019.sched.com/event/Sfq4/there-are-no-zero-co...
- rcxdude 7y ago
  Only if the deleter you define has any state, which is very rare and in that case you would need to copy that data around anyway... (for example: https://gcc.godbolt.org/z/mU7hub https://gcc.godbolt.org/z/mU7hub)
- pingyong 7y ago
  It's pretty stupid to compare a unique_ptr with a deleter that contains state to a pointer - obviously those two things are completely different and the unique_ptr contains way more information.

> Even std::unique_ptr has runtime costs in release builds that a raw pointer does not. O RLY ? https://gcc.godbolt.org/z/QhbUjI https://gcc.godbolt.org/z/QhbUjI

abainbridge 7y ago

How would I create the pointer to int in the unique_ptr case without initializing the int? I tried this: https://gcc.godbolt.org/z/SfVxzU https://gcc.godbolt.org/z/SfVxzU I expect there is a way, just I don't know it.

jcelerier 7y ago
See the docs : https://en.cppreference.com/w/cpp/memory/unique_ptr/make_unique https://en.cppreference.com/w/cpp/memory/unique_ptr/make_uni... For C++ < 20 replace `std::make_unique<int>()` by `std::unique_ptr<int>(new int)` (which with all explicit uses of `new` can end up not being safe in some cases (in that case, only if you've not enough memory to allocate an int which should not really be a common occurence...) For C++ >= 20 you get std::make_unique_default_init which does that properly.
- deleted 7y ago
  [deleted]
einpoklum 7y ago
Have created a Stackoverflow question focused on this point: https://stackoverflow.com/q/58050872/1593077 https://stackoverflow.com/q/58050872/1593077

Pombal 7y ago

Yes, really. It's fine for simple types but for more complex types in more complex situations, you pay the price. Unique pointers carry around not just the type but also a default deleter, if you provide one. That deleter has to be copied around, checked for nullptr before execution and set to nullptr when ownership changes. For even more examples of this have a look at this talk when it comes out: https://cppcon2019.sched.com/event/Sfq4/there-are-no-zero-cost-abstractions https://cppcon2019.sched.com/event/Sfq4/there-are-no-zero-co...

rcxdude 7y ago
Only if the deleter you define has any state, which is very rare and in that case you would need to copy that data around anyway... (for example: https://gcc.godbolt.org/z/mU7hub https://gcc.godbolt.org/z/mU7hub)
pingyong 7y ago
It's pretty stupid to compare a unique_ptr with a deleter that contains state to a pointer - obviously those two things are completely different and the unique_ptr contains way more information.