Print Options

All of these options are passed to rustc via the --print flag.

Those options prints out various information about the compiler. Multiple options can be specified, and the information is printed in the order the options are specified.

Specifying an option will usually disable the --emit step and will only print the requested information.

A filepath may optionally be specified for each requested information kind, in the format --print KIND=PATH, just like for --emit. When a path is specified, information will be written there instead of to stdout.

crate-name

The name of the crate.

Generally coming from either from the #![crate_name = "..."] attribute, --crate-name flag or the filename.

Example:

$ rustc --print crate-name --crate-name my_crate a.rs
my_crate

file-names

The names of the files created by the link emit kind.

sysroot

Absolute path to the sysroot.

Example (with rustup and the stable toolchain):

$ rustc --print sysroot a.rs
/home/[REDACTED]/.rustup/toolchains/stable-x86_64-unknown-linux-gnu

target-libdir

Path to the target libdir.

Example (with rustup and the stable toolchain):

$ rustc --print target-libdir a.rs
/home/[REDACTED]/.rustup/toolchains/beta-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib

host-tuple

The target-tuple string of the host compiler.

Example:

$ rustc --print host-tuple a.rs
x86_64-unknown-linux-gnu

Example with the --target flag:

$ rustc --print host-tuple --target "armv7-unknown-linux-gnueabihf" a.rs
x86_64-unknown-linux-gnu

cfg

List of cfg values. See conditional compilation for more information about cfg values.

Example (for x86_64-unknown-linux-gnu):

$ rustc --print cfg a.rs
debug_assertions
panic="unwind"
target_abi=""
target_arch="x86_64"
target_endian="little"
target_env="gnu"
target_family="unix"
target_feature="fxsr"
target_feature="sse"
target_feature="sse2"
target_has_atomic="16"
target_has_atomic="32"
target_has_atomic="64"
target_has_atomic="8"
target_has_atomic="ptr"
target_os="linux"
target_pointer_width="64"
target_vendor="unknown"
unix

target-list

List of known targets. The target may be selected with the --target flag.

target-cpus

List of available CPU values for the current target. The target CPU may be selected with the -C target-cpu=val flag.

target-features

List of available target features for the current target.

Target features may be enabled with the unsafe -C target-feature=val flag.

See known issues for more details.

relocation-models

List of relocation models. Relocation models may be selected with the -C relocation-model=val flag.

Example:

$ rustc --print relocation-models a.rs
Available relocation models:
    static
    pic
    pie
    dynamic-no-pic
    ropi
    rwpi
    ropi-rwpi
    default

code-models

List of code models. Code models may be selected with the -C code-model=val flag.

Example:

$ rustc --print code-models a.rs
Available code models:
    tiny
    small
    kernel
    medium
    large

tls-models

List of Thread Local Storage models supported. The model may be selected with the -Z tls-model=val flag.

Example:

$ rustc --print tls-models a.rs
Available TLS models:
    global-dynamic
    local-dynamic
    initial-exec
    local-exec
    emulated

native-static-libs

This may be used when creating a staticlib crate type.

If this is the only flag, it will perform a full compilation and include a diagnostic note that indicates the linker flags to use when linking the resulting static library.

The note starts with the text native-static-libs: to make it easier to fetch the output.

Example:

$ rustc --print native-static-libs --crate-type staticlib a.rs
note: link against the following native artifacts when linking against this static library. The order and any duplication can be significant on some platforms.

note: native-static-libs: -lgcc_s -lutil [REDACTED] -lpthread -lm -ldl -lc

link-args

This flag does not disable the --emit step. This can be useful when debugging linker options.

When linking, this flag causes rustc to print the full linker invocation in a human-readable form. The exact format of this debugging output is not a stable guarantee, other than that it will include the linker executable and the text of each command-line argument passed to the linker.

deployment-target

The currently selected deployment target (or minimum OS version) for the selected Apple platform target.

This value can be used or passed along to other components alongside a Rust build that need this information, such as C compilers. This returns rustc‘s minimum supported deployment target if no *_DEPLOYMENT_TARGET variable is present in the environment, or otherwise returns the variable’s parsed value.