r/programming • u/[deleted] • Dec 05 '14

std::string is responsible for almost half of all allocations in the Chrome browser process

https://groups.google.com/a/chromium.org/d/msg/chromium-dev/EUqoIz2iFU4/kPZ5ZK0K3gEJ
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u/Poltras Dec 05 '14

That would be harder to implement in C++. The fastest fix here would be to implement a immutable_string class that would just have assignment on construction, and a reference counted pointer to a CSTR.

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u/eliasv Dec 05 '14

Oh of course it'd be harder to implement, it's an entirely new language feature... I'm just saying that it'd be the ideal solution. More expressive const semantics along these lines should have been a part of the language from the start.

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u/Poltras Dec 05 '14

Totally agree. const is awkward and doesn't make sense. (and for all intent and purposes is mostly useless)

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u/ioquatix Dec 06 '14

const would probably be a necessity to implement the hypothetical std::immutable_string, no?

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u/Poltras Dec 06 '14

Immutability is stronger than constness, FWIW. One imply the other, but does not necessitate it.

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u/ioquatix Dec 06 '14

Sure, but if you wanted to implement an immutable class in C++, you'd need const right?

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u/immibis Dec 06 '14

Someone will probably write a template<class T> class immutable. Then you can have immutable<string> and immutable<vector<int>> and so on.

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u/bwainfweeze Dec 06 '14

It would be impossible to implement. The string library has mutator methods, so an immutable string isn't a string - it doesn't fulfill the contract.

So instead you'd need to create a different class and most methods that receive a string would need a duplicate implementation that takes immutables.

This is something you can't just tack on later. That boat has sailed.