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Implement libstd for CloudABI. #47268

Merged
merged 6 commits into from
Jan 14, 2018
Merged

Implement libstd for CloudABI. #47268

merged 6 commits into from
Jan 14, 2018

Commits on Jan 11, 2018

  1. Import the CloudABI system call bindings into the libstd tree. 

    These automatically generated Rust source files allow us to invoke
system calls within CloudABI processes. These will be used by libstd to
implement primitives for I/O, threading, etc.

These source files are normally part of the 'cloudabi' crate. In the
case of libstd, we'd better copy them into the source tree, as having
external dependencies in libstd is a bit messy. Original source files
can be found here:

    https://github.com/NuxiNL/cloudabi/tree/master/rust
    @EdSchouten
    EdSchouten committed Jan 11, 2018
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  2. Implement libstd for CloudABI. 

    Though CloudABI is strongly inspired by POSIX, its absence of features
that don't work well with capability-based sandboxing makes it different
enough that adding bits to sys/unix will make things a mess. This change
therefore adds CloudABI specific platform code under sys/cloudabi and
borrows parts from sys/unix that can be used without changes.

One of the goals of this implementation is to build as much as possible
directly on top of CloudABI's system call layer, as opposed to using the
C library. This is preferred, as the system call layer is supposed to be
stable, whereas the C library ABI technically is not. An advantage of
this approach is that it allows us to implement certain interfaces, such
as mutexes and condition variables more optimally. They can be lighter
than the ones provided by pthreads.

This change disables some modules that cannot realistically be
implemented right now. For example, libstd's pathname abstraction is not
designed with POSIX *at() (e.g., openat()) in mind. The *at() functions
are the only set of file system APIs available on CloudABI. There is no
global file system namespace, nor a process working directory.
Discussions on how to port these modules over are outside the scope of
this change.

Apart from this change, there are still some other minor fixups that
need to be made to platform independent code to make things build. These
will be sent out separately, so they can be reviewed more thoroughly.
    @EdSchouten
    EdSchouten committed Jan 11, 2018
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  3. Add shims for modules that we can't implement on CloudABI. 

    As discussed in rust-lang#47268, libstd isn't ready to have certain functionality
disabled yet. Follow wasm's approach of adding no-op modules for all of
the features that we can't implement.

I've placed all of those shims in a shims/ subdirectory, so we (the
CloudABI folks) can experiment with removing them more easily. It also
ensures that the code that does work doesn't get polluted with lots of
useless boilerplate code.
    @EdSchouten
    EdSchouten committed Jan 11, 2018
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  4. Make tests build on CloudABI. 

    There are some tests that need to be disabled on CloudABI specifically,
due to the fact that the shims cannot be built in combination with
unix::ext or windows::ext. Also improve the scoping of some imports to
suppress compiler warnings.
    @EdSchouten
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  5. Make the documentation build work on CloudABI. 

    Just like with wasm, we can't just import unix::ext and windows::ext.
Our shims are not complete enough for that.
    @EdSchouten
    EdSchouten committed Jan 11, 2018
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  6. Extend tidy to allow conditionalizing tests for multiple targets.

    @EdSchouten
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