f9fc49c06e
This change is an implementation of [RFC 69][rfc] which adds a third kind of
global to the language, `const`. This global is most similar to what the old
`static` was, and if you're unsure about what to use then you should use a
`const`.
The semantics of these three kinds of globals are:
* A `const` does not represent a memory location, but only a value. Constants
are translated as rvalues, which means that their values are directly inlined
at usage location (similar to a #define in C/C++). Constant values are, well,
constant, and can not be modified. Any "modification" is actually a
modification to a local value on the stack rather than the actual constant
itself.
Almost all values are allowed inside constants, whether they have interior
mutability or not. There are a few minor restrictions listed in the RFC, but
they should in general not come up too often.
* A `static` now always represents a memory location (unconditionally). Any
references to the same `static` are actually a reference to the same memory
location. Only values whose types ascribe to `Sync` are allowed in a `static`.
This restriction is in place because many threads may access a `static`
concurrently. Lifting this restriction (and allowing unsafe access) is a
future extension not implemented at this time.
* A `static mut` continues to always represent a memory location. All references
to a `static mut` continue to be `unsafe`.
This is a large breaking change, and many programs will need to be updated
accordingly. A summary of the breaking changes is:
* Statics may no longer be used in patterns. Statics now always represent a
memory location, which can sometimes be modified. To fix code, repurpose the
matched-on-`static` to a `const`.
static FOO: uint = 4;
match n {
FOO => { /* ... */ }
_ => { /* ... */ }
}
change this code to:
const FOO: uint = 4;
match n {
FOO => { /* ... */ }
_ => { /* ... */ }
}
* Statics may no longer refer to other statics by value. Due to statics being
able to change at runtime, allowing them to reference one another could
possibly lead to confusing semantics. If you are in this situation, use a
constant initializer instead. Note, however, that statics may reference other
statics by address, however.
* Statics may no longer be used in constant expressions, such as array lengths.
This is due to the same restrictions as listed above. Use a `const` instead.
[breaking-change]
Closes #17718
[rfc]: https://github.com/rust-lang/rfcs/pull/246
This is a preliminary version of the Rust compiler, libraries and tools.
Source layout:
| Path | Description |
|---|---|
librustc/ |
The self-hosted compiler |
liballoc/ |
Rust's core allocation library |
libcore/ |
The Rust core library |
libdebug/ |
Debugging utilities |
libstd/ |
The standard library (imported and linked by default) |
libgreen/ |
The M:N runtime library |
libnative/ |
The 1:1 runtime library |
libsyntax/ |
The Rust parser and pretty-printer |
libtest/ |
Rust's test-runner code |
| ------------------- | --------------------------------------------------------- |
libarena/ |
The arena (a fast but limited) memory allocator |
libbacktrace/ |
The libbacktrace library |
libcollections/ |
A collection of useful data structures and containers |
libflate/ |
Simple compression library |
libfmt_macros/ |
Macro support for format strings |
libfourcc/ |
Data format identifier library |
libgetopts/ |
Get command-line-options library |
libglob/ |
Unix glob patterns library |
libgraphviz/ |
Generating files for Graphviz |
libhexfloat/ |
Hexadecimal floating-point literals |
liblibc/ |
Bindings for the C standard library |
liblog/ |
Utilities for program-wide and customizable logging |
libnum/ |
Extended number support library (complex, rational, etc) |
librand/ |
Random numbers and distributions |
libregex/ |
Regular expressions |
libregex_macros/ |
The regex! syntax extension |
libsemver/ |
Rust's semantic versioning library |
libserialize/ |
Encode-Decode types library |
libsync/ |
Concurrency mechanisms and primitives |
libterm/ |
ANSI color library for terminals |
libtime/ |
Time operations library |
liburl/ |
URL handling lirary |
libuuid/ |
UUID's handling code |
| ------------------- | --------------------------------------------------------- |
rt/ |
The runtime system |
rt/rust_*.c |
- Some of the runtime services |
rt/vg |
- Valgrind headers |
rt/msvc |
- MSVC support |
rt/sundown |
- The Markdown library used by rustdoc |
| ------------------- | --------------------------------------------------------- |
compiletest/ |
The test runner |
test/ |
Testsuite |
test/codegen |
- Tests for the LLVM IR infrastructure |
test/compile-fail |
- Tests that should fail to compile |
test/debug-info |
- Tests for the debuginfo tool |
test/run-fail |
- Tests that should compile, run and fail |
test/run-make |
- Tests that depend on a Makefile infrastructure |
test/run-pass |
- Tests that should compile, run and succeed |
test/bench |
- Benchmarks and miscellaneous |
test/pretty |
- Pretty-printer tests |
test/auxiliary |
- Dependencies of tests |
| ------------------- | --------------------------------------------------------- |
librustdoc/ |
The Rust API documentation tool |
| ------------------- | --------------------------------------------------------- |
llvm/ |
The LLVM submodule |
rustllvm/ |
LLVM support code |
| ------------------- | --------------------------------------------------------- |
etc/ |
Scripts, editors support, misc |
NOTE: This list (especially the second part of the table which contains modules and libraries) is highly volatile and subject to change.