rust/config.toml.example

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# Sample TOML configuration file for building Rust.
#
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# To configure rustbuild, copy this file to the directory from which you will be
# running the build, and name it config.toml.
#
# All options are commented out by default in this file, and they're commented
# out with their default values. The build system by default looks for
# `config.toml` in the current directory of a build for build configuration, but
# a custom configuration file can also be specified with `--config` to the build
# system.
# =============================================================================
# Tweaking how LLVM is compiled
# =============================================================================
[llvm]
# Indicates whether the LLVM build is a Release or Debug build
#optimize = true
# Indicates whether LLVM should be built with ThinLTO. Note that this will
# only succeed if you use clang, lld, llvm-ar, and llvm-ranlib in your C/C++
# toolchain (see the `cc`, `cxx`, `linker`, `ar`, and `ranlib` options below).
# More info at: https://clang.llvm.org/docs/ThinLTO.html#clang-bootstrap
#thin-lto = false
# Indicates whether an LLVM Release build should include debug info
#release-debuginfo = false
# Indicates whether the LLVM assertions are enabled or not
#assertions = false
# Indicates whether ccache is used when building LLVM
#ccache = false
# or alternatively ...
#ccache = "/path/to/ccache"
# If an external LLVM root is specified, we automatically check the version by
# default to make sure it's within the range that we're expecting, but setting
# this flag will indicate that this version check should not be done.
#version-check = true
# Link libstdc++ statically into the librustc_llvm instead of relying on a
# dynamic version to be available.
#static-libstdcpp = false
# Tell the LLVM build system to use Ninja instead of the platform default for
# the generated build system. This can sometimes be faster than make, for
# example.
#ninja = false
# LLVM targets to build support for.
# Note: this is NOT related to Rust compilation targets. However, as Rust is
# dependent on LLVM for code generation, turning targets off here WILL lead to
# the resulting rustc being unable to compile for the disabled architectures.
# Also worth pointing out is that, in case support for new targets are added to
# LLVM, enabling them here doesn't mean Rust is automatically gaining said
# support. You'll need to write a target specification at least, and most
# likely, teach rustc about the C ABI of the target. Get in touch with the
# Rust team and file an issue if you need assistance in porting!
#targets = "X86;ARM;AArch64;Mips;PowerPC;SystemZ;MSP430;Sparc;NVPTX;Hexagon"
# LLVM experimental targets to build support for. These targets are specified in
# the same format as above, but since these targets are experimental, they are
# not built by default and the experimental Rust compilation targets that depend
# on them will not work unless the user opts in to building them. By default the
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# `WebAssembly` and `RISCV` targets are enabled when compiling LLVM from scratch.
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#experimental-targets = "WebAssembly;RISCV"
# Cap the number of parallel linker invocations when compiling LLVM.
# This can be useful when building LLVM with debug info, which significantly
# increases the size of binaries and consequently the memory required by
# each linker process.
# If absent or 0, linker invocations are treated like any other job and
# controlled by rustbuild's -j parameter.
#link-jobs = 0
# When invoking `llvm-config` this configures whether the `--shared` argument is
# passed to prefer linking to shared libraries.
#link-shared = false
# When building llvm, this configures what is being appended to the version.
# If absent, we let the version as-is.
#version-suffix = "-rust"
# On MSVC you can compile LLVM with clang-cl, but the test suite doesn't pass
# with clang-cl, so this is special in that it only compiles LLVM with clang-cl
#clang-cl = '/path/to/clang-cl.exe'
# Pass extra compiler and linker flags to the LLVM CMake build.
#cflags = "-fextra-flag"
#cxxflags = "-fextra-flag"
#ldflags = "-Wl,extra-flag"
# Use libc++ when building LLVM instead of libstdc++. This is the default on
# platforms already use libc++ as the default C++ library, but this option
# allows you to use libc++ even on platforms when it's not. You need to ensure
# that your host compiler ships with libc++.
#use-libcxx = true
# The value specified here will be passed as `-DLLVM_USE_LINKER` to CMake.
#use-linker = "lld"
# Whether or not to specify `-DLLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN=YES`
#allow-old-toolchain = false
# =============================================================================
# General build configuration options
# =============================================================================
[build]
# Build triple for the original snapshot compiler. This must be a compiler that
# nightlies are already produced for. The current platform must be able to run
# binaries of this build triple and the nightly will be used to bootstrap the
# first compiler.
#build = "x86_64-unknown-linux-gnu" # defaults to your host platform
# In addition to the build triple, other triples to produce full compiler
# toolchains for. Each of these triples will be bootstrapped from the build
# triple and then will continue to bootstrap themselves. This platform must
# currently be able to run all of the triples provided here.
#host = ["x86_64-unknown-linux-gnu"] # defaults to just the build triple
# In addition to all host triples, other triples to produce the standard library
# for. Each host triple will be used to produce a copy of the standard library
# for each target triple.
#target = ["x86_64-unknown-linux-gnu"] # defaults to just the build triple
# Instead of downloading the src/stage0.txt version of Cargo specified, use
# this Cargo binary instead to build all Rust code
#cargo = "/path/to/bin/cargo"
# Instead of downloading the src/stage0.txt version of the compiler
# specified, use this rustc binary instead as the stage0 snapshot compiler.
#rustc = "/path/to/bin/rustc"
# Flag to specify whether any documentation is built. If false, rustdoc and
# friends will still be compiled but they will not be used to generate any
# documentation.
#docs = true
# Indicate whether the compiler should be documented in addition to the standard
# library and facade crates.
#compiler-docs = false
# Indicate whether submodules are managed and updated automatically.
#submodules = true
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# Update submodules only when the checked out commit in the submodules differs
# from what is committed in the main rustc repo.
#fast-submodules = true
# The path to (or name of) the GDB executable to use. This is only used for
# executing the debuginfo test suite.
#gdb = "gdb"
# The node.js executable to use. Note that this is only used for the emscripten
# target when running tests, otherwise this can be omitted.
#nodejs = "node"
# Python interpreter to use for various tasks throughout the build, notably
# rustdoc tests, the lldb python interpreter, and some dist bits and pieces.
# Note that Python 2 is currently required.
#
# Defaults to python2.7, then python2. If neither executable can be found, then
# it defaults to the Python interpreter used to execute x.py.
#python = "python2.7"
# Force Cargo to check that Cargo.lock describes the precise dependency
# set that all the Cargo.toml files create, instead of updating it.
#locked-deps = false
# Indicate whether the vendored sources are used for Rust dependencies or not
#vendor = false
rustbuild: Compile rustc twice, not thrice This commit switches the rustbuild build system to compiling the compiler twice for a normal bootstrap rather than the historical three times. Rust is a bootstrapped language which means that a previous version of the compiler is used to build the next version of the compiler. Over time, however, we change many parts of compiler artifacts such as the metadata format, symbol names, etc. These changes make artifacts from one compiler incompatible from another compiler. Consequently if a compiler wants to be able to use some artifacts then it itself must have compiled the artifacts. Historically the rustc build system has achieved this by compiling the compiler three times: * An older compiler (stage0) is downloaded to kick off the chain. * This compiler now compiles a new compiler (stage1) * The stage1 compiler then compiles another compiler (stage2) * Finally, the stage2 compiler needs libraries to link against, so it compiles all the libraries again. This entire process amounts in compiling the compiler three times. Additionally, this process always guarantees that the Rust source tree can compile itself because the stage2 compiler (created by a freshly created compiler) would successfully compile itself again. This property, ensuring Rust can compile itself, is quite important! In general, though, this third compilation is not required for general purpose development on the compiler. The third compiler (stage2) can reuse the libraries that were created during the second compile. In other words, the second compilation can produce both a compiler and the libraries that compiler will use. These artifacts *must* be compatible due to the way plugins work today anyway, and they were created by the same source code so they *should* be compatible as well. So given all that, this commit switches the default build process to only compile the compiler three times, avoiding this third compilation by copying artifacts from the previous one. Along the way a new entry in the Travis matrix was also added to ensure that our full bootstrap can succeed. This entry does not run tests, though, as it should not be necessary. To restore the old behavior of a full bootstrap (three compiles) you can either pass: ./configure --enable-full-bootstrap or if you're using config.toml: [build] full-bootstrap = true Overall this will hopefully be an easy 33% win in build times of the compiler. If we do 33% less work we should be 33% faster! This in turn should affect cycle times and such on Travis and AppVeyor positively as well as making it easier to work on the compiler itself.
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# Typically the build system will build the rust compiler twice. The second
# compiler, however, will simply use its own libraries to link against. If you
# would rather to perform a full bootstrap, compiling the compiler three times,
# then you can set this option to true. You shouldn't ever need to set this
# option to true.
#full-bootstrap = false
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# Enable a build of the extended rust tool set which is not only the compiler
# but also tools such as Cargo. This will also produce "combined installers"
# which are used to install Rust and Cargo together. This is disabled by
# default.
#extended = false
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# Installs chosen set of extended tools if enables. By default builds all.
# If chosen tool failed to build the installation fails.
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#tools = ["cargo", "rls", "clippy", "rustfmt", "analysis", "src"]
# Verbosity level: 0 == not verbose, 1 == verbose, 2 == very verbose
#verbose = 0
# Build the sanitizer runtimes
#sanitizers = false
# Build the profiler runtime
#profiler = false
# Indicates whether the native libraries linked into Cargo will be statically
# linked or not.
#cargo-native-static = false
rustbuild: Add support for compiling Cargo This commit adds support to rustbuild for compiling Cargo as part of the release process. Previously rustbuild would simply download a Cargo snapshot and repackage it. With this change we should be able to turn off artifacts from the rust-lang/cargo repository and purely rely on the artifacts Cargo produces here. The infrastructure added here is intended to be extensible to other components, such as the RLS. It won't exactly be a one-line addition, but the addition of Cargo didn't require too much hooplah anyway. The process for release Cargo will now look like: * The rust-lang/rust repository has a Cargo submodule which is used to build a Cargo to pair with the rust-lang/rust release * Periodically we'll update the cargo submodule as necessary on rust-lang/rust's master branch * When branching beta we'll create a new branch of Cargo (as we do today), and the first commit to the beta branch will be to update the Cargo submodule to this exact revision. * When branching stable, we'll ensure that the Cargo submodule is updated and then make a stable release. Backports to Cargo will look like: * Send a PR to cargo's master branch * Send a PR to cargo's release branch (e.g. rust-1.16.0) * Send a PR to rust-lang/rust's beta branch updating the submodule * Eventually send a PR to rust-lang/rust's master branch updating the submodule For reference, the process to add a new component to the rust-lang/rust release would look like: * Add `$foo` as a submodule in `src/tools` * Add a `tool-$foo` step which compiles `$foo` with the specified compiler, likely mirroring what Cargo does. * Add a `dist-$foo` step which uses `src/tools/$foo` and the `tool-$foo` output to create a rust-installer package for `$foo` likely mirroring what Cargo does. * Update the `dist-extended` step with a new dependency on `dist-$foo` * Update `src/tools/build-manifest` for the new component.
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# Run the build with low priority, by setting the process group's "nice" value
# to +10 on Unix platforms, and by using a "low priority" job object on Windows.
#low-priority = false
# Arguments passed to the `./configure` script, used during distcheck. You
# probably won't fill this in but rather it's filled in by the `./configure`
# script.
#configure-args = []
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# Indicates that a local rebuild is occurring instead of a full bootstrap,
# essentially skipping stage0 as the local compiler is recompiling itself again.
#local-rebuild = false
# Print out how long each rustbuild step took (mostly intended for CI and
# tracking over time)
#print-step-timings = false
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# =============================================================================
# General install configuration options
# =============================================================================
[install]
# Instead of installing to /usr/local, install to this path instead.
#prefix = "/usr/local"
# Where to install system configuration files
# If this is a relative path, it will get installed in `prefix` above
#sysconfdir = "/etc"
# Where to install documentation in `prefix` above
#docdir = "share/doc/rust"
# Where to install binaries in `prefix` above
#bindir = "bin"
# Where to install libraries in `prefix` above
#libdir = "lib"
# Where to install man pages in `prefix` above
#mandir = "share/man"
# Where to install data in `prefix` above (currently unused)
#datadir = "share"
# Where to install additional info in `prefix` above (currently unused)
#infodir = "share/info"
# Where to install local state (currently unused)
# If this is a relative path, it will get installed in `prefix` above
#localstatedir = "/var/lib"
# =============================================================================
# Options for compiling Rust code itself
# =============================================================================
[rust]
# Whether or not to optimize the compiler and standard library.
#
# Note: the slowness of the non optimized compiler compiling itself usually
# outweighs the time gains in not doing optimizations, therefore a
# full bootstrap takes much more time with `optimize` set to false.
#optimize = true
# Indicates that the build should be configured for debugging Rust. A
# `debug`-enabled compiler and standard library will be somewhat
# slower (due to e.g. checking of debug assertions) but should remain
# usable.
#
# Note: If this value is set to `true`, it will affect a number of
# configuration options below as well, if they have been left
# unconfigured in this file.
#
# Note: changes to the `debug` setting do *not* affect `optimize`
# above. In theory, a "maximally debuggable" environment would
# set `optimize` to `false` above to assist the introspection
# facilities of debuggers like lldb and gdb. To recreate such an
# environment, explicitly set `optimize` to `false` and `debug`
# to `true`. In practice, everyone leaves `optimize` set to
# `true`, because an unoptimized rustc with debugging
# enabled becomes *unusably slow* (e.g. rust-lang/rust#24840
# reported a 25x slowdown) and bootstrapping the supposed
# "maximally debuggable" environment (notably libstd) takes
# hours to build.
#
#debug = false
# Number of codegen units to use for each compiler invocation. A value of 0
# means "the number of cores on this machine", and 1+ is passed through to the
# compiler.
#codegen-units = 1
# Sets the number of codegen units to build the standard library with,
# regardless of what the codegen-unit setting for the rest of the compiler is.
#codegen-units-std = 1
# Whether or not debug assertions are enabled for the compiler and standard
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# library.
#debug-assertions = false
# Whether or not debuginfo is emitted
#debuginfo = false
# Whether or not line number debug information is emitted
#debuginfo-lines = false
rustbuild: Don't enable debuginfo in rustc In #37280 we enabled line number debugging information in release artifacts, primarily to close out #36452 where debugging information was critical for MSVC builds of Rust to be useful in production. This commit, however, apparently had some unfortunate side effects. Namely it was noticed in #37477 that if `RUST_BACKTRACE=1` was set then any compiler error would take a very long time for the compiler to exit. The cause of the problem here was somewhat deep: * For all compiler errors, the compiler will `panic!` with a known value. This tears down the main compiler thread and allows cleaning up all the various resources. By default, however, this panic output is suppressed for "normal" compiler errors. * When `RUST_BACKTRACE=1` was set this caused every compiler error to generate a backtrace. * The libbacktrace library hits a pathological case where it spends a very long time in its custom allocation function, `backtrace_alloc`, because the compiler has so much debugging information. More information about this can be found in #29293 with a summary at the end of #37477. To solve this problem this commit simply removes debuginfo from the compiler but not from the standard library. This should allow us to keep #36452 closed while also closing #37477. I've measured the difference to be orders of magnitude faster than it was before, so we should see a much quicker time-to-exit after a compile error when `RUST_BACKTRACE=1` is set. Closes #37477 Closes #37571
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# Whether or not to only build debuginfo for the standard library if enabled.
# If enabled, this will not compile the compiler with debuginfo, just the
# standard library.
#debuginfo-only-std = false
# Enable debuginfo for the extended tools: cargo, rls, rustfmt
# Adding debuginfo makes them several times larger.
#debuginfo-tools = false
# Whether or not `panic!`s generate backtraces (RUST_BACKTRACE)
#backtrace = true
# Whether to always use incremental compilation when building rustc
#incremental = false
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# Build a multi-threaded rustc
#parallel-compiler = false
# The default linker that will be hard-coded into the generated compiler for
# targets that don't specify linker explicitly in their target specifications.
# Note that this is not the linker used to link said compiler.
#default-linker = "cc"
# The "channel" for the Rust build to produce. The stable/beta channels only
# allow using stable features, whereas the nightly and dev channels allow using
# nightly features
#channel = "dev"
# By default the `rustc` executable is built with `-Wl,-rpath` flags on Unix
# platforms to ensure that the compiler is usable by default from the build
# directory (as it links to a number of dynamic libraries). This may not be
# desired in distributions, for example.
#rpath = true
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# Emits extraneous output from tests to ensure that failures of the test
# harness are debuggable just from logfiles.
#verbose-tests = false
# Flag indicating whether tests are compiled with optimizations (the -O flag) or
# with debuginfo (the -g flag)
#optimize-tests = true
#debuginfo-tests = true
# Flag indicating whether codegen tests will be run or not. If you get an error
# saying that the FileCheck executable is missing, you may want to disable this.
# Also see the target's llvm-filecheck option.
#codegen-tests = true
# Flag indicating whether git info will be retrieved from .git automatically.
# Having the git information can cause a lot of rebuilds during development.
# Note: If this attribute is not explicitly set (e.g. if left commented out) it
# will default to true if channel = "dev", but will default to false otherwise.
#ignore-git = true
# When creating source tarballs whether or not to create a source tarball.
#dist-src = false
# Whether to also run the Miri tests suite when running tests.
# As a side-effect also generates MIR for all libraries.
#test-miri = false
# After building or testing extended tools (e.g. clippy and rustfmt), append the
# result (broken, compiling, testing) into this JSON file.
#save-toolstates = "/path/to/toolstates.json"
rustc: Split Emscripten to a separate codegen backend This commit introduces a separately compiled backend for Emscripten, avoiding compiling the `JSBackend` target in the main LLVM codegen backend. This builds on the foundation provided by #47671 to create a new codegen backend dedicated solely to Emscripten, removing the `JSBackend` of the main codegen backend in the process. A new field was added to each target for this commit which specifies the backend to use for translation, the default being `llvm` which is the main backend that we use. The Emscripten targets specify an `emscripten` backend instead of the main `llvm` one. There's a whole bunch of consequences of this change, but I'll try to enumerate them here: * A *second* LLVM submodule was added in this commit. The main LLVM submodule will soon start to drift from the Emscripten submodule, but currently they're both at the same revision. * Logic was added to rustbuild to *not* build the Emscripten backend by default. This is gated behind a `--enable-emscripten` flag to the configure script. By default users should neither check out the emscripten submodule nor compile it. * The `init_repo.sh` script was updated to fetch the Emscripten submodule from GitHub the same way we do the main LLVM submodule (a tarball fetch). * The Emscripten backend, turned off by default, is still turned on for a number of targets on CI. We'll only be shipping an Emscripten backend with Tier 1 platforms, though. All cross-compiled platforms will not be receiving an Emscripten backend yet. This commit means that when you download the `rustc` package in Rustup for Tier 1 platforms you'll be receiving two trans backends, one for Emscripten and one that's the general LLVM backend. If you never compile for Emscripten you'll never use the Emscripten backend, so we may update this one day to only download the Emscripten backend when you add the Emscripten target. For now though it's just an extra 10MB gzip'd. Closes #46819
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# This is an array of the codegen backends that will be compiled for the rustc
# that's being compiled. The default is to only build the LLVM codegen backend,
# but you can also optionally enable the "emscripten" backend for asm.js or
# make this an empty array (but that probably won't get too far in the
# bootstrap)
#codegen-backends = ["llvm"]
# This is the name of the directory in which codegen backends will get installed
#codegen-backends-dir = "codegen-backends"
# Flag indicating whether `libstd` calls an imported function to handle basic IO
# when targeting WebAssembly. Enable this to debug tests for the `wasm32-unknown-unknown`
# target, as without this option the test output will not be captured.
#wasm-syscall = false
rust: Import LLD for linking wasm objects This commit imports the LLD project from LLVM to serve as the default linker for the `wasm32-unknown-unknown` target. The `binaryen` submoule is consequently removed along with "binaryen linker" support in rustc. Moving to LLD brings with it a number of benefits for wasm code: * LLD is itself an actual linker, so there's no need to compile all wasm code with LTO any more. As a result builds should be *much* speedier as LTO is no longer forcibly enabled for all builds of the wasm target. * LLD is quickly becoming an "official solution" for linking wasm code together. This, I believe at least, is intended to be the main supported linker for native code and wasm moving forward. Picking up support early on should help ensure that we can help LLD identify bugs and otherwise prove that it works great for all our use cases! * Improvements to the wasm toolchain are currently primarily focused around LLVM and LLD (from what I can tell at least), so it's in general much better to be on this bandwagon for bugfixes and new features. * Historical "hacks" like `wasm-gc` will soon no longer be necessary, LLD will [natively implement][gc] `--gc-sections` (better than `wasm-gc`!) which means a postprocessor is no longer needed to show off Rust's "small wasm binary size". LLD is added in a pretty standard way to rustc right now. A new rustbuild target was defined for building LLD, and this is executed when a compiler's sysroot is being assembled. LLD is compiled against the LLVM that we've got in tree, which means we're currently on the `release_60` branch, but this may get upgraded in the near future! LLD is placed into rustc's sysroot in a `bin` directory. This is similar to where `gcc.exe` can be found on Windows. This directory is automatically added to `PATH` whenever rustc executes the linker, allowing us to define a `WasmLd` linker which implements the interface that `wasm-ld`, LLD's frontend, expects. Like Emscripten the LLD target is currently only enabled for Tier 1 platforms, notably OSX/Windows/Linux, and will need to be installed manually for compiling to wasm on other platforms. LLD is by default turned off in rustbuild, and requires a `config.toml` option to be enabled to turn it on. Finally the unstable `#![wasm_import_memory]` attribute was also removed as LLD has a native option for controlling this. [gc]: https://reviews.llvm.org/D42511
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# Indicates whether LLD will be compiled and made available in the sysroot for
# rustc to execute.
#lld = false
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# Indicates whether some LLVM tools, like llvm-objdump, will be made available in the
# sysroot.
#llvm-tools = false
# Indicates whether LLDB will be made available in the sysroot.
# This is only built if LLVM is also being built.
#lldb = false
# Whether to deny warnings in crates
#deny-warnings = true
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# Print backtrace on internal compiler errors during bootstrap
#backtrace-on-ice = false
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# Whether to verify generated LLVM IR
#verify-llvm-ir = false
# Map all debuginfo paths for libstd and crates to `/rust/$sha/$crate/...`,
# generally only set for releases
#remap-debuginfo = false
# Link the compiler against `jemalloc`, where on Linux and OSX it should
# override the default allocator for rustc and LLVM.
#jemalloc = false
# Run tests in various test suites with the "nll compare mode" in addition to
# running the tests in normal mode. Largely only used on CI and during local
# development of NLL
#test-compare-mode = false
# Use LLVM libunwind as the implementation for Rust's unwinder.
#llvm-libunwind = false
# =============================================================================
# Options for specific targets
#
# Each of the following options is scoped to the specific target triple in
# question and is used for determining how to compile each target.
# =============================================================================
[target.x86_64-unknown-linux-gnu]
# C compiler to be used to compiler C code. Note that the
# default value is platform specific, and if not specified it may also depend on
# what platform is crossing to what platform.
#cc = "cc"
# C++ compiler to be used to compiler C++ code (e.g. LLVM and our LLVM shims).
# This is only used for host targets.
#cxx = "c++"
# Archiver to be used to assemble static libraries compiled from C/C++ code.
# Note: an absolute path should be used, otherwise LLVM build will break.
#ar = "ar"
# Ranlib to be used to assemble static libraries compiled from C/C++ code.
# Note: an absolute path should be used, otherwise LLVM build will break.
#ranlib = "ranlib"
# Linker to be used to link Rust code. Note that the
# default value is platform specific, and if not specified it may also depend on
# what platform is crossing to what platform.
#linker = "cc"
# Path to the `llvm-config` binary of the installation of a custom LLVM to link
# against. Note that if this is specified we don't compile LLVM at all for this
# target.
#llvm-config = "../path/to/llvm/root/bin/llvm-config"
# Normally the build system can find LLVM's FileCheck utility, but if
# not, you can specify an explicit file name for it.
#llvm-filecheck = "/path/to/FileCheck"
# If this target is for Android, this option will be required to specify where
# the NDK for the target lives. This is used to find the C compiler to link and
# build native code.
#android-ndk = "/path/to/ndk"
# Force static or dynamic linkage of the standard library for this target. If
# this target is a host for rustc, this will also affect the linkage of the
# compiler itself. This is useful for building rustc on targets that normally
# only use static libraries. If unset, the target's default linkage is used.
#crt-static = false
# The root location of the MUSL installation directory. The library directory
# will also need to contain libunwind.a for an unwinding implementation. Note
# that this option only makes sense for MUSL targets that produce statically
# linked binaries
#musl-root = "..."
Add a new wasm32-unknown-wasi target This commit adds a new wasm32-based target distributed through rustup, supported in the standard library, and implemented in the compiler. The `wasm32-unknown-wasi` target is intended to be a WebAssembly target which matches the [WASI proposal recently announced.][LINK]. In summary the WASI target is an effort to define a standard set of syscalls for WebAssembly modules, allowing WebAssembly modules to not only be portable across architectures but also be portable across environments implementing this standard set of system calls. The wasi target in libstd is still somewhat bare bones. This PR does not fill out the filesystem, networking, threads, etc. Instead it only provides the most basic of integration with the wasi syscalls, enabling features like: * `Instant::now` and `SystemTime::now` work * `env::args` is hooked up * `env::vars` will look up environment variables * `println!` will print to standard out * `process::{exit, abort}` should be hooked up appropriately None of these APIs can work natively on the `wasm32-unknown-unknown` target, but with the assumption of the WASI set of syscalls we're able to provide implementations of these syscalls that engines can implement. Currently the primary engine implementing wasi is [wasmtime], but more will surely emerge! In terms of future development of libstd, I think this is something we'll probably want to discuss. The purpose of the WASI target is to provide a standardized set of syscalls, but it's *also* to provide a standard C sysroot for compiling C/C++ programs. This means it's intended that functions like `read` and `write` are implemented for this target with a relatively standard definition and implementation. It's unclear, therefore, how we want to expose file descriptors and how we'll want to implement system primitives. For example should `std::fs::File` have a libc-based file descriptor underneath it? The raw wasi file descriptor? We'll see! Currently these details are all intentionally hidden and things we can change over time. A `WasiFd` sample struct was added to the standard library as part of this commit, but it's not currently used. It shows how all the wasi syscalls could be ergonomically bound in Rust, and they offer a possible implementation of primitives like `std::fs::File` if we bind wasi file descriptors exactly. Apart from the standard library, there's also the matter of how this target is integrated with respect to its C standard library. The reference sysroot, for example, provides managment of standard unix file descriptors and also standard APIs like `open` (as opposed to the relative `openat` inspiration for the wasi ssycalls). Currently the standard library relies on the C sysroot symbols for operations such as environment management, process exit, and `read`/`write` of stdio fds. We want these operations in Rust to be interoperable with C if they're used in the same process. Put another way, if Rust and C are linked into the same WebAssembly binary they should work together, but that requires that the same C standard library is used. We also, however, want the `wasm32-unknown-wasi` target to be usable-by-default with the Rust compiler without requiring a separate toolchain to get downloaded and configured. With that in mind, there's two modes of operation for the `wasm32-unknown-wasi` target: 1. By default the C standard library is statically provided inside of `liblibc.rlib` distributed as part of the sysroot. This means that you can `rustc foo.wasm --target wasm32-unknown-unknown` and you're good to go, a fully workable wasi binary pops out. This is incompatible with linking in C code, however, which may be compiled against a different sysroot than the Rust code was previously compiled against. In this mode the default of `rust-lld` is used to link binaries. 2. For linking with C code, the `-C target-feature=-crt-static` flag needs to be passed. This takes inspiration from the musl target for this flag, but the idea is that you're no longer using the provided static C runtime, but rather one will be provided externally. This flag is intended to also get coupled with an external `clang` compiler configured with its own sysroot. Therefore you'll typically use this flag with `-C linker=/path/to/clang-script-wrapper`. Using this mode the Rust code will continue to reference standard C symbols, but the definition will be pulled in by the linker configured. Alright so that's all the current state of this PR. I suspect we'll definitely want to discuss this before landing of course! This PR is coupled with libc changes as well which I'll be posting shortly. [LINK]: [wasmtime]:
2019-02-13 19:02:22 +01:00
# The root location of the `wasm32-unknown-wasi` sysroot.
#wasi-root = "..."
# Used in testing for configuring where the QEMU images are located, you
# probably don't want to use this.
#qemu-rootfs = "..."
# =============================================================================
# Distribution options
#
# These options are related to distribution, mostly for the Rust project itself.
# You probably won't need to concern yourself with any of these options
# =============================================================================
[dist]
# This is the folder of artifacts that the build system will sign. All files in
# this directory will be signed with the default gpg key using the system `gpg`
# binary. The `asc` and `sha256` files will all be output into the standard dist
# output folder (currently `build/dist`)
#
# This folder should be populated ahead of time before the build system is
# invoked.
#sign-folder = "path/to/folder/to/sign"
# This is a file which contains the password of the default gpg key. This will
# be passed to `gpg` down the road when signing all files in `sign-folder`
# above. This should be stored in plaintext.
#gpg-password-file = "path/to/gpg/password"
# The remote address that all artifacts will eventually be uploaded to. The
# build system generates manifests which will point to these urls, and for the
# manifests to be correct they'll have to have the right URLs encoded.
#
# Note that this address should not contain a trailing slash as file names will
# be appended to it.
#upload-addr = "https://example.com/folder"
# Whether to build a plain source tarball to upload
# We disable that on Windows not to override the one already uploaded on S3
# as the one built on Windows will contain backslashes in paths causing problems
# on linux
#src-tarball = true
#
# Whether to allow failures when building tools
#missing-tools = false