locale allocation in std::basic_streambuf

[Dramcryx]

The project I am working with does not permit STL's default allocator for specific reasons, so for all string and container types we have alias with custom allocator implemented.

I wanted to make use of std::streambuf to implement a blob stream buffer that is compatible with the STL streams (e.g. std::istream), but it turned out that a default locale is constructed via new.
I see that for debug builds new for locale objects is overridden with malloc/free but what about release builds?

So how safe is that to go with derivation of std::streambuf? Are there any ABI or other historical reasons which required locale in std::streambuf to be allocated with new rather than default class member that libc++ and libstdc++ make use of?

std::stringstream allows for custom allocator but I cannot make use of it because I want to control exact memory allocations in stream buffer to avoid excess on them.

[StephanTLavavej]

I see that for debug builds new for locale objects is overridden with malloc/free but what about release builds?

It's not overridden for release builds. We use global new/delete normally.

So how safe is that to go with derivation of std::streambuf?

I don't understand the question.

Are there any ABI or other historical reasons which required locale in std::streambuf to be allocated with new rather than default class member

Historical reason: That's the way that Dinkumware, the original authors of our STL implementation, did it. Their rationale is lost to time.

ABI: Because this affects the representation of std::streambuf, we are utterly unable to change how this works in the v14 (VS 2015+) binary-compatible release series, so the question of why it was written this way is essentially academic, since we can't change it.

basic_spanbuf in <spanstream> was recently added, but it still inherits from basic_streambuf and therefore contains its _Plocale(new locale) data member.

The C++ Standard Library quite naturally assumes that it can use the C++ Core Language, of which new is an essential part.