Module layout 

Management of the directory layout of a build

The directory layout is a little tricky at times, hence a separate file to house this logic. Cargo stores build artifacts in two directories: artifact-dir and build-dir

artifact-dir layout

artifact-dir is where final artifacts like binaries are stored. The artifact-dir layout is consider part of the public API and cannot be easily changed.

<artifact-dir>/

    # Compilation files are grouped by build target and profile.
    # The target is omitted if not explicitly specified.
    [<target>]/<profile>/ # e.g. `debug` / `release`

        # File used to lock the directory to prevent multiple cargo processes
        # from using it at the same time.
        .cargo-lock

        # Root directory for all compiled examples.
        examples/

    # Output from rustdoc
    doc/

    # Output from `cargo package` to build a `.crate` file.
    package/

build-dir layout

build-dir is where intermediate build artifacts are stored. The build-dir layout is considered an internal implementation detail of Cargo meaning that we can change this if needed. However, in reality many tools rely on implementation details of Cargo so breaking changes need to be done carefully.

<build-dir>/

    # Cache of `rustc -Vv` output for performance.
    .rustc-info.json

    # Compilation files are grouped by build target and profile.
    # The target is omitted if not explicitly specified.
    [<target>]/<profile>/ # e.g. `debug` / `release`

        # File used to lock the directory to prevent multiple cargo processes
        # from using it at the same time.
        .cargo-lock

        # Hidden directory that holds all of the fingerprint files for all
        # packages
        .fingerprint/
            # Each package is in a separate directory.
            # Note that different target kinds have different filename prefixes.
            $pkgname-$META/
                # Set of source filenames for this package.
                dep-lib-$targetname
                # Timestamp when this package was last built.
                invoked.timestamp
                # The fingerprint hash.
                lib-$targetname
                # Detailed information used for logging the reason why
                # something is being recompiled.
                lib-$targetname.json
                # The console output from the compiler. This is cached
                # so that warnings can be redisplayed for "fresh" units.
                output-lib-$targetname

        # This is the root directory for all rustc artifacts except build
        # scripts, examples, and test and bench executables. Almost every
        # artifact should have a metadata hash added to its filename to
        # prevent collisions. One notable exception is dynamic libraries.
        deps/

            # Each artifact dependency gets in its own directory.
            /artifact/$pkgname-$META/$kind

        # Root directory for all compiled examples.
        examples/

        # Directory used to store incremental data for the compiler (when
        # incremental is enabled.
        incremental/

        # This is the location at which the output of all custom build
        # commands are rooted.
        build/

            # Each package gets its own directory where its build script and
            # script output are placed
            $pkgname-$META/    # For the build script itself.
                # The build script executable (name may be changed by user).
                build-script-build-$META
                # Hard link to build-script-build-$META.
                build-script-build
                # Dependency information generated by rustc.
                build-script-build-$META.d
                # Debug information, depending on platform and profile
                # settings.
                <debug symbols>

            # The package shows up twice with two different metadata hashes.
            $pkgname-$META/  # For the output of the build script.
                # Timestamp when the build script was last executed.
                invoked.timestamp
                # Directory where script can output files ($OUT_DIR).
                out/
                # Output from the build script.
                output
                # Path to `out`, used to help when the target directory is
                # moved.
                root-output
                # Stderr output from the build script.
                stderr

    # Used by `cargo package` and `cargo publish` to build a `.crate` file.
    package/

    # Experimental feature for generated build scripts.
    .metabuild/

New build-dir layout

build-dir supports a new “build unit” based layout that is unstable. It can be enabled via -Zbuild-dir-new-layout. For more info about the layout transition see: #15010

<build-dir>/

    # Cache of `rustc -Vv` output for performance.
    .rustc-info.json

    # Compilation files are grouped by build target and profile.
    # The target is omitted if not explicitly specified.
    [<target>]/<profile>/ # e.g. `debug` / `release`

        # File used to lock the directory to prevent multiple cargo processes
        # from using it at the same time.
        .cargo-lock

        # Directory used to store incremental data for the compiler (when
        # incremental is enabled.
        incremental/

        # Main directory for storing build unit related files.
        # Files are organized by Cargo build unit (`$pkgname/$META`) so that
        # related files are stored in a single directory.
        build/

            # This is the location at which the output of all files related to
            # a given build unit. These files are organized together so that we can
            # treat this directly like a single unit for locking and caching.
            $pkgname/
                $META/
                    # The general purpose output directory for build units.
                    # For compilation units, the rustc artifact will be located here.
                    # For build script run units, this is the $OUT_DIR
                    out/

                        # For artifact dependency units, the output is nested by the kind
                        artifact/$kind

                    # Directory that holds all of the fingerprint files for the build unit.
                    fingerprint/
                        # Set of source filenames for this package.
                        dep-lib-$targetname
                        # Timestamp when this package was last built.
                        invoked.timestamp
                        # The fingerprint hash.
                        lib-$targetname
                        # Detailed information used for logging the reason why
                        # something is being recompiled.
                        lib-$targetname.json
                        # The console output from the compiler. This is cached
                        # so that warnings can be redisplayed for "fresh" units.
                        output-lib-$targetname

                    # Directory for "execution" units that spawn a process (excluding compilation with
                    # rustc). Contains the process execution details.
                    # Currently the only execution unit Cargo supports is running build script
                    # binaries.
                    run/
                        # Timestamp of last execution.
                        invoked.timestamp
                        # Stdout output from the process.
                        stdout
                        # Stderr output from the process.
                        stderr
                        # Path to `out`, used to help when the target directory is
                        # moved. (build scripts)
                        root-output

    # Used by `cargo package` and `cargo publish` to build a `.crate` file.
    package/

    # Experimental feature for generated build scripts.
    .metabuild/

When cross-compiling, the layout is the same, except it appears in target/$TRIPLE.

Structs

ArtifactDirLayout

BuildDirLayout

Layout

Contains the paths of all target output locations.