The low-level C++ dynamic memory allocation API is ridiculously bloated:
en.cppreference.com/w/cpp/memory/n
A global allocator has 8 variants of operator new to implement and 12 for operator delete. In total, there are 22 variants of operator new and 26 for operator delete (4 more soon).
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It doesn't even offer any form of reallocation, let alone good control over it. The useless std::nothrow_t variants of delete for symmetry with new are a bit funny. They didn't end up adding those for sized allocation as initially planned, so at least they avoided 4 more deletes.
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The configurable hook added in C++11 for freeing memory and triggering a retry at the allocator layer is neat, but real world programs would want to do it at the malloc layer. It only makes sense at this layer if it was a different allocator, which would make very little sense...
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Reallocation would be so nice, but we'd have to get guarantees that non-POD classes are relocatable in memory, right?
Right now, most classes can be memcpy-ed to a new location (just no destructors on old), but only guarantees are made for is_trivially_copyable.
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From what I remember, you're basically safe as long as the class doesn't have a pointer to in-class data, or is virtual (since despite every compiler using a vtable, the implementation is never specified). But still... realllocation without relocatable data is... tricky.
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It could fully support it for these low-level replaceable functions, since it doesn't have types. There could be a variant that's allowed to relocate along with a variant that's not allowed to do that. It could then be used when possible by higher-level APIs if it existed here.
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Yeah. Definitely true. It's also such a glaring flaw that many C++ libraries design their own allocators using malloc/free and then define a trait `is_relocatable` just for that purpose.
github.com/facebook/folly
I don't consider C++ worth improving but they certainly could have wired up the infrastructure for more efficient reallocation. It's pretty sad that std::vector can't do proper reallocation under the hood when the types can support it because infrastructure for it isn't present.
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I don't feel it's worth trying to improve C++ at this point though. It's too much of a bloated disaster and doesn't serve the purpose of providing a shared compatible ABI and runtime like C. Extending the malloc API would be useful in the long term but this thing is a lost cause.
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