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extern types #1861

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merged 19 commits into from
Jul 25, 2017
Merged

extern types #1861

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6085dc4
Add extern types RFC
canndrew Jan 21, 2017
b2d8042
One sentance per line so future diffs are readable. 2 and typo fixes too
Ericson2314 Jan 21, 2017
e6f7f93
Expand teaching section
Ericson2314 Jan 21, 2017
083adad
Shout-out to roadmap with it's focus on FFI in the motivation section
Ericson2314 Jan 21, 2017
2f77316
Add ```rust in a few more places to get syntax highlighting
Ericson2314 Jan 21, 2017
949c292
Mention `size_of_val`/`align_of_val` in detailed design
Ericson2314 Jan 21, 2017
9f6d098
OOps
Ericson2314 Jan 21, 2017
cf183e9
"Sized" is the trait, not "?Sized"
Ericson2314 Jan 21, 2017
434b472
Talk about `c_void`, and associated representation concerns
Ericson2314 Jan 21, 2017
b3d5ba3
Merge pull request #1 from Ericson2314/extern-types
canndrew Jan 21, 2017
bce8a7b
Grammatic changes
canndrew Jan 21, 2017
156ed4b
Remove indentation and invalid syntax
canndrew Jan 21, 2017
caa048b
Fix typo
canndrew Jan 23, 2017
d76b608
Mention OpaqueData as an alternative
canndrew Jan 27, 2017
a590767
grammar/typos
canndrew Apr 30, 2017
9efddd3
Update with feedback
canndrew Apr 30, 2017
263b7c9
Clarify that extern type pointers are thin pointers
canndrew Jul 24, 2017
e884a0b
re-word last commit
canndrew Jul 25, 2017
4b971bd
RFC 1861 is Extern types
aturon Jul 25, 2017
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2 changes: 1 addition & 1 deletion text/0000-extern-types.md
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Expand Up @@ -64,7 +64,7 @@ These types are FFI-safe. They are also DSTs, meaning that they do not implement
In Rust, pointers to DSTs carry metadata about the object being pointed to.
For strings and slices this is the length of the buffer, for trait objects this is the object's vtable.
For extern types the metadata is simply `()`.
This means that a pointer to an extern type is identical to a raw pointer.
This means that a pointer to an extern type is identical to a raw pointer (ie. it is not a "fat pointer").
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Probably better to just say it is not a fat pointer and not even bother bringing up raw pointers because raw pointers can be fat too! *const [T] is fat for example despite being a raw pointer.

It also means that if we store an extern type at the end of a container (such as a struct or tuple) pointers to that container will also be identical to raw pointers (despite the container as a whole being unsized).
This is useful to support a pattern found in some C APIs where structs are passed around which have arbitrary data appended to the end of them: eg.

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