{ lib, stdenv, pkgsBuildHost, pkgsBuildTarget, pkgsTargetTarget }:

rec {
  # These environment variables must be set when using `cargo-c` and
  # several other tools which do not deal well with cross
  # compilation.  The symptom of the problem they fix is errors due
  # to buildPlatform CFLAGS being passed to the
  # hostPlatform-targeted compiler -- for example, `-m64` being
  # passed on a build=x86_64/host=aarch64 compilation.
  envVars = let

    # As a workaround for https://github.com/rust-lang/rust/issues/89626 use lld on pkgsStatic aarch64
    shouldUseLLD = platform:
      platform.isAarch64 && platform.isStatic && !stdenv.isDarwin;

    ccForBuild =
      "${pkgsBuildHost.stdenv.cc}/bin/${pkgsBuildHost.stdenv.cc.targetPrefix}cc";
    cxxForBuild =
      "${pkgsBuildHost.stdenv.cc}/bin/${pkgsBuildHost.stdenv.cc.targetPrefix}c++";
    linkerForBuild = ccForBuild;

    ccForHost = "${stdenv.cc}/bin/${stdenv.cc.targetPrefix}cc";
    cxxForHost = "${stdenv.cc}/bin/${stdenv.cc.targetPrefix}c++";
    linkerForHost =
      if shouldUseLLD stdenv.targetPlatform && !stdenv.cc.bintools.isLLVM then
        "${pkgsBuildHost.llvmPackages.bintools}/bin/${stdenv.cc.targetPrefix}ld.lld"
      else
        ccForHost;

    # Unfortunately we must use the dangerous `pkgsTargetTarget` here
    # because hooks are artificially phase-shifted one slot earlier
    # (they go in nativeBuildInputs, so the hostPlatform looks like
    # a targetPlatform to them).
    ccForTarget =
      "${pkgsTargetTarget.stdenv.cc}/bin/${pkgsTargetTarget.stdenv.cc.targetPrefix}cc";
    cxxForTarget =
      "${pkgsTargetTarget.stdenv.cc}/bin/${pkgsTargetTarget.stdenv.cc.targetPrefix}c++";
    linkerForTarget = if shouldUseLLD pkgsTargetTarget.stdenv.targetPlatform
    && !pkgsTargetTarget.stdenv.cc.bintools.isLLVM # whether stdenv's linker is lld already
    then
      "${pkgsBuildTarget.llvmPackages.bintools}/bin/${pkgsTargetTarget.stdenv.cc.targetPrefix}ld.lld"
    else
      ccForTarget;

    rustBuildPlatform = stdenv.buildPlatform.rust.rustcTarget;
    rustBuildPlatformSpec = stdenv.buildPlatform.rust.rustcTargetSpec;
    rustHostPlatform = stdenv.hostPlatform.rust.rustcTarget;
    rustHostPlatformSpec = stdenv.hostPlatform.rust.rustcTargetSpec;
    rustTargetPlatform = stdenv.targetPlatform.rust.rustcTarget;
    rustTargetPlatformSpec = stdenv.targetPlatform.rust.rustcTargetSpec;
  in {
    inherit ccForBuild cxxForBuild linkerForBuild rustBuildPlatform
      rustBuildPlatformSpec ccForHost cxxForHost linkerForHost rustHostPlatform
      rustHostPlatformSpec ccForTarget cxxForTarget linkerForTarget
      rustTargetPlatform rustTargetPlatformSpec;

    # Prefix this onto a command invocation in order to set the
    # variables needed by cargo.
    #
    setEnv = ''
      env \
    ''
      # Due to a bug in how splicing and pkgsTargetTarget works, in
      # situations where pkgsTargetTarget is irrelevant
      # pkgsTargetTarget.stdenv.cc is often simply wrong.  We must omit
      # the following lines when rustTargetPlatform collides with
      # rustHostPlatform.
      + lib.optionalString (rustTargetPlatform != rustHostPlatform) ''
        "CC_${stdenv.targetPlatform.rust.cargoEnvVarTarget}=${ccForTarget}" \
        "CXX_${stdenv.targetPlatform.rust.cargoEnvVarTarget}=${cxxForTarget}" \
        "CARGO_TARGET_${stdenv.targetPlatform.rust.cargoEnvVarTarget}_LINKER=${linkerForTarget}" \
      '' + ''
        "CC_${stdenv.hostPlatform.rust.cargoEnvVarTarget}=${ccForHost}" \
        "CXX_${stdenv.hostPlatform.rust.cargoEnvVarTarget}=${cxxForHost}" \
        "CARGO_TARGET_${stdenv.hostPlatform.rust.cargoEnvVarTarget}_LINKER=${linkerForHost}" \
      '' + ''
        "CC_${stdenv.buildPlatform.rust.cargoEnvVarTarget}=${ccForBuild}" \
        "CXX_${stdenv.buildPlatform.rust.cargoEnvVarTarget}=${cxxForBuild}" \
        "CARGO_TARGET_${stdenv.buildPlatform.rust.cargoEnvVarTarget}_LINKER=${linkerForBuild}" \
        "CARGO_BUILD_TARGET=${rustBuildPlatform}" \
        "HOST_CC=${pkgsBuildHost.stdenv.cc}/bin/cc" \
        "HOST_CXX=${pkgsBuildHost.stdenv.cc}/bin/c++" \
      '';
  };
} // lib.mapAttrs (old: new: platform:
  # TODO: enable warning after 23.05 is EOL.
  # lib.warn "`rust.${old} platform` is deprecated. Use `platform.rust.${new}` instead."
  lib.getAttrFromPath new platform.rust) {
    toTargetArch = [ "platform" "arch" ];
    toTargetOs = [ "platform" "os" ];
    toTargetFamily = [ "platform" "target-family" ];
    toTargetVendor = [ "platform" "vendor" ];
    toRustTarget = [ "rustcTarget" ];
    toRustTargetSpec = [ "rustcTargetSpec" ];
    toRustTargetSpecShort = [ "cargoShortTarget" ];
    toRustTargetForUseInEnvVars = [ "cargoEnvVarTarget" ];
    IsNoStdTarget = [ "isNoStdTarget" ];
  }