Module build::output

Outputs from the build script, in the form of cargo: printed lines.

Does not print a leading newline. Thus, if you ever write to stdout and don’t lock until a trailing newline, these instructions will likely fail.

Functions

rerun_if_changed

The rerun-if-changed instruction tells Cargo to re-run the build script if the file at the given path has changed. Currently, Cargo only uses the filesystem last-modified “mtime” timestamp to determine if the file has changed. It compares against an internal cached timestamp of when the build script last ran.

rerun_if_env_changed

The rerun-if-env-changed instruction tells Cargo to re-run the build script if the value of an environment variable of the given name has changed.

rustc_cdylib_link_arg

The rustc-cdylib-link-arg instruction tells Cargo to pass the -C link-arg=FLAG option to the compiler, but only when building a cdylib library target. Its usage is highly platform specific. It is useful to set the shared library version or the runtime-path.

rustc_cfg

The rustc-cfg instruction tells Cargo to pass the given value to the --cfg flag to the compiler. This may be used for compile-time detection of features to enable conditional compilation.

rustc_cfg_value

See rustc_cfg.

rustc_env

The rustc-env instruction tells Cargo to set the given environment variable when compiling the package. The value can be then retrieved by the env! macro in the compiled crate. This is useful for embedding additional metadata in crate’s code, such as the hash of git HEAD or the unique identifier of a continuous integration server.

rustc_flags

The rustc-flags instruction tells Cargo to pass the given space-separated flags to the compiler. This only allows the -l and -L flags, and is equivalent to using rustc-link-lib and rustc-link-search.

rustc_link_arg

The rustc-link-arg instruction tells Cargo to pass the -C link-arg=FLAG option to the compiler, but only when building supported targets (benchmarks, binaries, cdylib crates, examples, and tests). Its usage is highly platform specific. It is useful to set the shared library version or linker script.

rustc_link_arg_bin

The rustc-link-arg-bin instruction tells Cargo to pass the -C link-arg=FLAG option to the compiler, but only when building the binary target with name BIN. Its usage is highly platform specific. It is useful to set a linker script or other linker options.

rustc_link_arg_bins

The rustc-link-arg-bins instruction tells Cargo to pass the -C link-arg=FLAG option to the compiler, but only when building a binary target. Its usage is highly platform specific. It is useful to set a linker script or other linker options.

rustc_link_lib

The rustc-link-lib instruction tells Cargo to link the given library using the compiler’s -l flag. This is typically used to link a native library using [FFI].

rustc_link_lib_kind

See rustc_link_lib.

rustc_link_search

The rustc-link-search instruction tells Cargo to pass the -L flag to the compiler to add a directory to the library search path.

rustc_link_search_kind

See rustc_link_search.

warning

The warning instruction tells Cargo to display a warning after the build script has finished running. Warnings are only shown for path dependencies (that is, those you’re working on locally), so for example warnings printed out in crates.io crates are not emitted by default. The -vv “very verbose” flag may be used to have Cargo display warnings for all crates.