Reuse `sys::unix::cmath` on other platforms
Reuse `sys::unix::cmath` on all non-`windows` platforms.
`unix` is chosen as the canonical location instead of `unsupported` or `common` because `unsupported` doesn't make sense semantically and `common` is reserved for code that is supported on all platforms. Also `unix` is already the home of some non-`windows` code that is technically not exclusive to `unix` like `unix::path`.
Make the libstd build script smaller
Of all sysroot crates currently only compiler_builtins, miniz_oxide and std require a build script. compiler_builtins uses to conditionally enable certain features and possibly compile a C version ([source](63ccaf11f0/build.rs)), miniz_oxide only uses it to detect if liballoc is supported as the MSRV is 1.34.0 instead of the 1.36.0 which stabilized liballoc ([source](28514ec09f/miniz_oxide/build.rs)). std now only uses it to enable `freebsd12` when the `RUST_STD_FREEBSD_12_ABI` env var is set, to determine if `restricted-std` should be set, to set the `STD_ENV_ARCH` env var identical to `CARGO_CFG_TARGET_ARCH`, and to unconditionally enable `backtrace_in_libstd`.
If all build scripts were to be removed, it would be possible for rustc to completely compile it's own sysroot. It currently requires a rustc version that already has an available libstd to compile the build scripts. If rustc can completely compile it's own sysroot, rustbuild could be simplified to not forcefully use the bootstrap compiler for build scripts.
`@rustbot` modify labels: +T-compiler +libs-impl
If pthread mutex initialization fails, the failure will go unnoticed unless
debug assertions are enabled. Any subsequent use of mutex will also silently
fail, since return values from lock & unlock operations are similarly checked
only through debug assertions.
In some implementations the mutex initialization requires a memory
allocation and so it does fail in practice.
Check that initialization succeeds to ensure that mutex guarantees
mutual exclusion.
Use futex-based thread::park/unpark on Linux.
This moves the parking/unparking logic out of `thread/mod.rs` into a module named `thread_parker` in `sys_common`. The current implementation is moved to `sys_common/thread_parker/generic.rs` and the new implementation using futexes is added in `sys_common/thread_parker/futex.rs`.
The syscalls returning a new file descriptors generally use
lowest-numbered file descriptor not currently opened, without any
exceptions for those corresponding to the standard streams.
Previously when any of standard streams has been closed before starting
the application, operations on std::io::{stderr,stdin,stdout} objects
were likely to operate on other logically unrelated file resources
opened afterwards.
Avoid the issue by reopening the standard streams when they are closed.
