3 ms·

> If you don't care about heap allocations then why are you using C++ :) Because more often than not it is a made-up problem that at best is classified as prem

by rewmie 3y ago

> If you don't care about heap allocations then why are you using C++ :) Because more often than not it is a made-up problem that at best is classified as premature optimization. Take, for example, Qt and how it uses it's UI form classes. You can include it's autogenerated code by composition, inheritance, and through a pimpl. You are here complaining that everyone should care about heap allocations. Well, in this case they happen only at app start and behind a standard C++ smart pointer, and it's basically only used to instantiate a factory to create UI elements. Can you tell me exactly any concrete reason why anyone should care about instantiating a few bytes in the heap with a smart pointer at app start? Sometimes there are real problems,but sometimes there are made-up problems that have no relevance or meaning.

vvanders 3y ago
I've had to deal with fragmentation at some point or another across most titles I've shipped or larger programs. Small allocations are actually worse in some ways because they incur a lot of fine-grained fragmentation. My favorite was logic in a fairly well-known game engine that would allocate a generic name for an entity and then immediately rename it to something unique. That 5 byte allocation would be left behind multiplied by every entity cost us ~30mb of a 256mb fixed memory address space. If you don't deal in those sorts of domains that's fine but don't dismiss them as those are some of the primary use cases for native languages. Pimpl is a hack, it's a clever hack in the context of C++ but it's not something intrinsic to native development. For instance it's a non-concern for languages like Rust(which just handle this whole domain much better due to not having to inherit a bunch of legacy behavior). There's a bunch of feedback in adjacent threads that you seem to be ignoring so I suspect I won't change your mind here but I would encourage you to be a bit more open and consider that there are use cases where things like this matter rather than dismissing them offhand.

by rewmie 3y ago

vvanders 3y ago

I've had to deal with fragmentation at some point or another across most titles I've shipped or larger programs. Small allocations are actually worse in some ways because they incur a lot of fine-grained fragmentation. My favorite was logic in a fairly well-known game engine that would allocate a generic name for an entity and then immediately rename it to something unique. That 5 byte allocation would be left behind multiplied by every entity cost us ~30mb of a 256mb fixed memory address space. If you don't deal in those sorts of domains that's fine but don't dismiss them as those are some of the primary use cases for native languages. Pimpl is a hack, it's a clever hack in the context of C++ but it's not something intrinsic to native development. For instance it's a non-concern for languages like Rust(which just handle this whole domain much better due to not having to inherit a bunch of legacy behavior). There's a bunch of feedback in adjacent threads that you seem to be ignoring so I suspect I won't change your mind here but I would encourage you to be a bit more open and consider that there are use cases where things like this matter rather than dismissing them offhand.