alloc support (for no_std environments) #256
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Feature gates anything dependent on `std` on the eponymous cargo feature, and changes references to libcore features from `std` to `core`
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| #[cfg(feature = "std")] | ||
| impl<'a> IntoBuf for &'a mut [u8] { | ||
| type Buf = io::Cursor<&'a mut [u8]>; |
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To really support alloc properly I think these impls (both this one and the one below for &'a str need to change to not use an io::Cursor), however as Buf is an associated type, I imagine it's considered part of the public API and changes to the underlying Buf type would be considered breaking. As a breaking change I think ideally we could fix this by eliminating all usages of io::Cursor from the crate (which, I believe, was @carllerche's plan for v0.5.x anyway).
However I'd like to stress that even without these impls, bytes + alloc is still useful, because downstream no_std + alloc consumers of bytes can define their own buffer type (possibly just vendoring io::Cursor from libstd and using the existing std-dependent impls) and then impl FromBuf and impl IntoBuf for their own type. This would be my planned approach for now if this PR were to be merged.
| pub use alloc::vec::Vec; | ||
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| #[cfg(feature = "std")] | ||
| pub use std::prelude::v1::*; |
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This looks a little bit weird because it pulls these types in from different places depending on the precise set of features enabled, so it doesn't look purely additive, however std just re-exports the alloc types as a facade, so it winds up being purely additive.
Ideally we could always pull the types in from alloc, and completely get rid of this module, however that would depend on alloc stabilization and would therefore be a breaking change in the minimum supported Rust version.
Gates all allocator-dependent features on the 'alloc' cargo feature, allowing use in no_std environments which have a heap and defined allocator, but not full support for 'std'.
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Thanks. At this point, focus is shifting towards the next breaking release. I’ll aim to get this included. |
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Please take a look at #269, my design proposal to abstract away the allocator. |
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@mzabaluev Looks good to me! I'd support that approach over what's in this PR |
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Obsoleted by #281 |
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This PR revives #153 and includes #255. I'm reopening it because the
alloccrate is now stable, which should hopefully address the previous concerns about #153 beingnightly-dependent.It gates all allocator-dependent features on the
alloccargo feature, enabling use of much of the functionality inno_stdenvironments which have a heap and defined allocator, but not full support for 'std'.Unlike previous attempts, this PR runs the parts of the test suite which do not require
stdas part of CI, ensuring thatallocsupport is properly tested. For now this requiresnightly, but whenallocstabilization lands in thestablechannel, it should be possible to always testallocsupport in all environments.