Enforce the shadowing restrictions from RFC 1560 for today's macros
This PR enforces a weakened version of the shadowing restrictions from RFC 1560. More specifically,
- If a macro expansion contains a `macro_rules!` macro definition that is used outside of the expansion, the defined macro may not shadow an existing macro.
- If a macro expansion contains a `#[macro_use] extern crate` macro import that is used outside of the expansion, the imported macro may not shadow an existing macro.
This is a [breaking-change]. For example,
```rust
macro_rules! m { () => {} }
macro_rules! n { () => {
macro_rules! m { () => {} } //< This shadows an existing macro.
m!(); //< This is inside the expansion that generated `m`'s definition, so it is OK.
} }
n!();
m!(); //< This use of `m` is outside the expansion, so it causes the shadowing to be an error.
```
r? @nrc
The two branches of this `if` compute the same value. This commit gets
rid of the first branch, which makes this calculation identical to the
one in scan_block_comment().
First, assert! is redundant w.r.t. the unwrap() immediately afterwards.
Second, `byte_offset_diff` is effectively computed as
`current_byte_offset + ch.len_utf8() - current_byte_offset` (with `next`
as an intermediate) which is silly and can be simplified.
This commit avoids the `resolve_type_vars_if_possible` call in
`plug_leaks` when `skol_map` is empty, which is the common case. It also
changes the signature of `plug_leaks` slightly to avoid the need for a
`clone` of `value`. These changes give speed-ups of up a few percent on
some of the rustc-benchmarks.
This commit avoids the `fold_regions` call in `plug_leaks` when
`skol_map` is empty, which is the common case. This gives speed-ups of
up to 1.14x on some of the rustc-benchmarks.
Restrict where in the tree platform-specific cfgs may be mentioned
With the ports of Rust never ending, it's important that we keep things tidy. The main thing this PR does is introduce a new "pal" (platform abstraction layer) tidy check that limits where platform-specific CFGs may appear.
This is intended to maintain existing standards of code organization
in hopes that the standard library will continue to be refactored to
isolate platform-specific bits, making porting easier; where "standard
library" roughly means "all the dependencies of the std and test
crates".
This generally means placing restrictions on where `cfg(unix)`,
`cfg(windows)`, `cfg(target_os)` and `cfg(target_env)` may appear,
the basic objective being to isolate platform-specific code to the
platform-specific `std::sys` modules, and to the allocation,
unwinding, and libc crates.
Following are the basic rules, though there are currently
exceptions:
- core may not have platform-specific code
- liballoc_system may have platform-specific code
- liballoc_jemalloc may have platform-specific code
- libpanic_abort may have platform-specific code
- libpanic_unwind may have platform-specific code
- other crates in the std facade may not
- std may have platform-specific code in the following places
- sys/unix/
- sys/windows/
- os/
There are plenty of exceptions today though, noted in the whitelist.
The end-state, IMO, is for the standard library to be portable by porting only `std::sys` (possibly extracted to its own crate), an allocator crate, an unwinder crate, and possibly a libc crate (if std depends on it); but that outcome is far off and independent of the utility of enforcing where such code lives today.
cc @rust-lang/libs
As it stands, getting-started and guessing-game both introduce `run` as
a new command. The second should probably make it clear that the reader
has seen it before :)
This is intended to maintain existing standards of code organization
in hopes that the standard library will continue to be refactored to
isolate platform-specific bits, making porting easier; where "standard
library" roughly means "all the dependencies of the std and test
crates".
This generally means placing restrictions on where `cfg(unix)`,
`cfg(windows)`, `cfg(target_os)` and `cfg(target_env)` may appear,
the basic objective being to isolate platform-specific code to the
platform-specific `std::sys` modules, and to the allocation,
unwinding, and libc crates.
Following are the basic rules, though there are currently
exceptions:
- core may not have platform-specific code
- liballoc_system may have platform-specific code
- liballoc_jemalloc may have platform-specific code
- libpanic_abort may have platform-specific code
- libpanic_unwind may have platform-specific code
- other crates in the std facade may not
- std may have platform-specific code in the following places
- sys/unix/
- sys/windows/
- os/
There are plenty of exceptions today though, noted in the whitelist.
Refactor layout to store offsets of fields, not offsets after fields
This is the next PR moving us towards being able to reorder struct fields.
The old code implicitly stored the offset of the first field. This is inadequate because the first field may no longer be offset 0 in future. This PR refactors `layout` to use a `offsets` vector instead of a `offset_after_field` vector.
this commit adds 4 new target definitions to the compiler for easier
cross compilation to ARM Cortex-M devices.
- `thumbv6m-none-eabi`
- For the Cortex-M0, Cortex-M0+ and Cortex-M1
- This architecture doesn't have hardware support (instructions) for
atomics. Hence, the `Atomic*` structs are not available for this
target.
- `thumbv7m-none-eabi`
- For the Cortex-M3
- `thumbv7em-none-eabi`
- For the FPU-less variants of the Cortex-M4 and Cortex-M7
- On this target, all the floating point operations will be lowered
software routines (intrinsics)
- `thumbv7em-none-eabihf`
- For the variants of the Cortex-M4 and Cortex-M7 that do have a FPU.
- On this target, all the floating point operations will be lowered
to hardware instructions
No binary releases of standard crates, like `core`, are planned for
these targets because Cargo, in the future, will compile e.g. the `core`
crate on the fly as part of the `cargo build` process. In the meantime,
you'll have to compile the `core` crate yourself. [Xargo] is the easiest
way to do that as in handles the compilation of `core` automatically and
can be used just like Cargo: `xargo build --target thumbv6m-none-eabi`
is all that's needed.
[Xargo]: https://crates.io/crates/xargo
Documentation change to macros.rs for `includes!`
I'm not sure if this documentation is clear or extensive enough, but this is just to get started on the problem, fixes issue #36387.
