Expand description
Flexible target specification.
Rust targets a wide variety of usecases, and in the interest of flexibility, allows new target tuples to be defined in configuration files. Most users will not need to care about these, but this is invaluable when porting Rust to a new platform, and allows for an unprecedented level of control over how the compiler works.
§Using custom targets
A target tuple, as passed via rustc --target=TUPLE
, will first be
compared against the list of built-in targets. This is to ease distributing
rustc (no need for configuration files) and also to hold these built-in
targets as immutable and sacred. If TUPLE
is not one of the built-in
targets, rustc will check if a file named TUPLE
exists. If it does, it
will be loaded as the target configuration. If the file does not exist,
rustc will search each directory in the environment variable
RUST_TARGET_PATH
for a file named TUPLE.json
. The first one found will
be loaded. If no file is found in any of those directories, a fatal error
will be given.
Projects defining their own targets should use
--target=path/to/my-awesome-platform.json
instead of adding to
RUST_TARGET_PATH
.
§Defining a new target
Targets are defined using JSON. The Target
struct in
this module defines the format the JSON file should take, though each
underscore in the field names should be replaced with a hyphen (-
) in the
JSON file. Some fields are required in every target specification, such as
llvm-target
, target-endian
, target-pointer-width
, data-layout
,
arch
, and os
. In general, options passed to rustc with -C
override
the target’s settings, though target-feature
and link-args
will add
to the list specified by the target, rather than replace.
Modules§
- base 🔒
- Object files providing support for basic runtime facilities and added to the produced binaries at the start and at the end of linking.
- json 🔒
- targets 🔒
Macros§
- cvs 🔒Cow-Vec-Str: Cow<’static, [Cow<’static, str>]>
Structs§
- The
-C link-self-contained
components that can individually be enabled or disabled. - The
-Z linker-features
components that can individually be enabled or disabled. - Everything
rustc
knows about how to compile for a specific target. - Metadata about a target like the description or tier. Part of #120745. All fields are optional for now, but intended to be required in the future.
- Optional aspects of a target specification.
- Warnings encountered when parsing the target
json
. - x86 (32-bit) abi options.
Enums§
- Linker is called through a C/C++ compiler.
- Which kind of debuginfo does the target use?
- Everything is flattened to a single enum to make the json encoding/decoding less annoying.
- The different
-Clink-self-contained
options that can be specified in a target spec: - All linkers have some kinds of command line interfaces and rustc needs to know which commands to use with each of them. So we cluster all such interfaces into a (somewhat arbitrary) number of classes that we call “linker flavors”.
- Linker flavors available externally through command line (
-Clinker-flavor
) or json target specifications. This set has accumulated historically, and contains both (stable and unstable) legacy values, as well as modern ones matching the internal linker flavors (LinkerFlavor
). - Linker is LLD.
- Controls use of stack canaries.
- For the
Target::check_consistency
function, determines whether the given target is a builtin or a JSON target. - Either a target tuple string or a path to a JSON file.
- Which C ABI to use for
wasm32-unknown-unknown
.
Constants§
- List of supported targets
Traits§
Functions§
- Add arguments for the given flavor and also for its “twin” flavors that have a compatible command line interface.
- Resolve the value of the EF_AVR_ARCH field for AVR ELF files, given the name of the target CPU / MCU.