rust: hooks: fix cross compilation

pkgs/build-support/rust/hooks/cargo-build-hook.sh

@@ -30,13 +30,8 @@ cargoBuildHook() {
 
     (
     set -x
-    env \
-      "CC_@rustBuildPlatform@=@ccForBuild@" \
-      "CXX_@rustBuildPlatform@=@cxxForBuild@" \
-      "CC_@rustTargetPlatform@=@ccForHost@" \
-      "CXX_@rustTargetPlatform@=@cxxForHost@" \
-      cargo build -j $NIX_BUILD_CORES \
-        --target @rustTargetPlatformSpec@ \
+    @setEnv@ cargo build -j $NIX_BUILD_CORES \
+        --target @rustHostPlatformSpec@ \
         --frozen \
         ${cargoBuildProfileFlag} \
         ${cargoBuildNoDefaultFeaturesFlag} \

pkgs/build-support/rust/hooks/cargo-check-hook.sh

@@ -29,7 +29,7 @@ cargoCheckHook() {
     fi
 
     argstr="${cargoCheckProfileFlag} ${cargoCheckNoDefaultFeaturesFlag} ${cargoCheckFeaturesFlag}
-        --target @rustTargetPlatformSpec@ --frozen ${cargoTestFlags}"
+        --target @rustHostPlatformSpec@ --frozen ${cargoTestFlags}"
 
     (
         set -x

pkgs/build-support/rust/hooks/cargo-install-hook.sh

@@ -1,7 +1,7 @@
 cargoInstallPostBuildHook() {
     echo "Executing cargoInstallPostBuildHook"
 
-    releaseDir=target/@shortTarget@/$cargoBuildType
+    releaseDir=target/@targetSubdirectory@/$cargoBuildType
     tmpDir="${releaseDir}-tmp";
 
     mkdir -p $tmpDir
@@ -21,7 +21,7 @@ cargoInstallHook() {
 
     # rename the output dir to a architecture independent one
 
-    releaseDir=target/@shortTarget@/$cargoBuildType
+    releaseDir=target/@targetSubdirectory@/$cargoBuildType
     tmpDir="${releaseDir}-tmp";
 
     mapfile -t targets < <(find "$NIX_BUILD_TOP" -type d | grep "${tmpDir}$")

pkgs/build-support/rust/hooks/cargo-nextest-hook.sh

@@ -29,7 +29,7 @@ cargoNextestHook() {
     fi
 
     argstr="${cargoCheckProfileFlag} ${cargoCheckNoDefaultFeaturesFlag} ${cargoCheckFeaturesFlag}
-        --target @rustTargetPlatformSpec@ --frozen ${cargoTestFlags}"
+        --target @rustHostPlatformSpec@ --frozen ${cargoTestFlags}"
 
     (
         set -x

pkgs/build-support/rust/hooks/default.nix

@@ -9,6 +9,10 @@
 , rust
 , rustc
 , stdenv
+
+# This confusingly-named parameter indicates the *subdirectory of
+# `target/` from which to copy the build artifacts.  It is derived
+# from a stdenv platform (or a JSON file; see below).
 , target ? rust.toRustTargetSpec stdenv.hostPlatform
 }:
 
@@ -17,24 +21,17 @@ let
 
   # see https://github.com/rust-lang/cargo/blob/964a16a28e234a3d397b2a7031d4ab4a428b1391/src/cargo/core/compiler/compile_kind.rs#L151-L168
   # the "${}" is needed to transform the path into a /nix/store path before baseNameOf
-  shortTarget = if targetIsJSON then
+  targetSubdirectory = if targetIsJSON then
       (lib.removeSuffix ".json" (builtins.baseNameOf "${target}"))
     else target;
-  ccForBuild = "${buildPackages.stdenv.cc}/bin/${buildPackages.stdenv.cc.targetPrefix}cc";
-  cxxForBuild = "${buildPackages.stdenv.cc}/bin/${buildPackages.stdenv.cc.targetPrefix}c++";
-  ccForHost = "${stdenv.cc}/bin/${stdenv.cc.targetPrefix}cc";
-  cxxForHost = "${stdenv.cc}/bin/${stdenv.cc.targetPrefix}c++";
-  rustBuildPlatform = rust.toRustTarget stdenv.buildPlatform;
-  rustTargetPlatform = rust.toRustTarget stdenv.hostPlatform;
-  rustTargetPlatformSpec = rust.toRustTargetSpec stdenv.hostPlatform;
+
 in {
   cargoBuildHook = callPackage ({ }:
     makeSetupHook {
       name = "cargo-build-hook.sh";
       propagatedBuildInputs = [ cargo ];
       substitutions = {
-        inherit ccForBuild ccForHost cxxForBuild cxxForHost
-          rustBuildPlatform rustTargetPlatform rustTargetPlatformSpec;
+        inherit (rust.envVars) rustHostPlatformSpec setEnv;
       };
     } ./cargo-build-hook.sh) {};
 
@@ -43,7 +40,7 @@ in {
       name = "cargo-check-hook.sh";
       propagatedBuildInputs = [ cargo ];
       substitutions = {
-        inherit rustTargetPlatformSpec;
+        inherit (rust.envVars) rustHostPlatformSpec;
       };
     } ./cargo-check-hook.sh) {};
 
@@ -52,7 +49,7 @@ in {
       name = "cargo-install-hook.sh";
       propagatedBuildInputs = [ ];
       substitutions = {
-        inherit shortTarget;
+        inherit targetSubdirectory;
       };
     } ./cargo-install-hook.sh) {};
 
@@ -61,7 +58,7 @@ in {
       name = "cargo-nextest-hook.sh";
       propagatedBuildInputs = [ cargo cargo-nextest ];
       substitutions = {
-        inherit rustTargetPlatformSpec;
+        inherit (rust.envVars) rustHostPlatformSpec;
       };
     } ./cargo-nextest-hook.sh) {};
 
@@ -78,23 +75,26 @@ in {
 
         cargoConfig = ''
           [target."${rust.toRustTarget stdenv.buildPlatform}"]
-          "linker" = "${ccForBuild}"
-          ${lib.optionalString (stdenv.buildPlatform.config != stdenv.hostPlatform.config) ''
-            [target."${shortTarget}"]
-            "linker" = "${ccForHost}"
+          "linker" = "${rust.envVars.ccForBuild}"
+          ${lib.optionalString (stdenv.hostPlatform.config != stdenv.targetPlatform.config) ''
+            [target."${rust.toRustTarget stdenv.targetPlatform}"]
+            "linker" = "${rust.envVars.ccForTarget}"
           ''}
           "rustflags" = [ "-C", "target-feature=${if stdenv.hostPlatform.isStatic then "+" else "-"}crt-static" ]
         '';
       };
     } ./cargo-setup-hook.sh) {};
 
-  maturinBuildHook = callPackage ({ }:
+  maturinBuildHook = callPackage ({ pkgsHostTarget }:
     makeSetupHook {
       name = "maturin-build-hook.sh";
-      propagatedBuildInputs = [ cargo maturin rustc ];
+      propagatedBuildInputs = [
+        pkgsHostTarget.maturin
+        pkgsHostTarget.cargo
+        pkgsHostTarget.rustc
+      ];
       substitutions = {
-        inherit ccForBuild ccForHost cxxForBuild cxxForHost
-          rustBuildPlatform rustTargetPlatform rustTargetPlatformSpec;
+        inherit (rust.envVars) rustTargetPlatformSpec setEnv;
       };
     } ./maturin-build-hook.sh) {};
 

pkgs/build-support/rust/hooks/maturin-build-hook.sh

@@ -9,12 +9,7 @@ maturinBuildHook() {
 
     (
     set -x
-    env \
-      "CC_@rustBuildPlatform@=@ccForBuild@" \
-      "CXX_@rustBuildPlatform@=@cxxForBuild@" \
-      "CC_@rustTargetPlatform@=@ccForHost@" \
-      "CXX_@rustTargetPlatform@=@cxxForHost@" \
-      maturin build \
+    @setEnv@ maturin build \
         --jobs=$NIX_BUILD_CORES \
         --frozen \
         --target @rustTargetPlatformSpec@ \

pkgs/build-support/rust/lib/default.nix

@@ -1,4 +1,8 @@
-{ lib }:
+{ lib
+, stdenv
+, buildPackages
+, targetPackages
+}:
 
 rec {
   # https://doc.rust-lang.org/reference/conditional-compilation.html#target_arch
@@ -59,8 +63,79 @@ rec {
     then builtins.toFile (toRustTarget platform + ".json") (builtins.toJSON platform.rustc.platform)
     else toRustTarget platform;
 
+  # When used as part of an environment variable name, triples are
+  # uppercased and have all hyphens replaced by underscores:
+  #
+  # https://github.com/rust-lang/cargo/pull/9169
+  # https://github.com/rust-lang/cargo/issues/8285#issuecomment-634202431
+  #
+  toRustTargetForUseInEnvVars = platform:
+    lib.strings.replaceStrings ["-"] ["_"]
+      (lib.strings.toUpper
+        (toRustTarget platform));
+
   # Returns true if the target is no_std
   # https://github.com/rust-lang/rust/blob/2e44c17c12cec45b6a682b1e53a04ac5b5fcc9d2/src/bootstrap/config.rs#L415-L421
   IsNoStdTarget = platform: let rustTarget = toRustTarget platform; in
     builtins.any (t: lib.hasInfix t rustTarget) ["-none" "nvptx" "switch" "-uefi"];
+
+  # 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
+    ccForBuild = "${buildPackages.stdenv.cc}/bin/${buildPackages.stdenv.cc.targetPrefix}cc";
+    cxxForBuild = "${buildPackages.stdenv.cc}/bin/${buildPackages.stdenv.cc.targetPrefix}c++";
+    ccForHost = "${stdenv.cc}/bin/${stdenv.cc.targetPrefix}cc";
+    cxxForHost = "${stdenv.cc}/bin/${stdenv.cc.targetPrefix}c++";
+
+    # Unfortunately we must use the dangerous `targetPackages` here
+    # because hooks are artificially phase-shifted one slot earlier
+    # (they go in nativeBuildInputs, so the hostPlatform looks like
+    # a targetPlatform to them).
+    ccForTarget = "${targetPackages.stdenv.cc}/bin/${targetPackages.stdenv.cc.targetPrefix}cc";
+    cxxForTarget = "${targetPackages.stdenv.cc}/bin/${targetPackages.stdenv.cc.targetPrefix}c++";
+
+    rustBuildPlatform = toRustTarget stdenv.buildPlatform;
+    rustBuildPlatformSpec = toRustTargetSpec stdenv.buildPlatform;
+    rustHostPlatform = toRustTarget stdenv.hostPlatform;
+    rustHostPlatformSpec = toRustTargetSpec stdenv.hostPlatform;
+    rustTargetPlatform = toRustTarget stdenv.targetPlatform;
+    rustTargetPlatformSpec = toRustTargetSpec stdenv.targetPlatform;
+  in {
+    inherit
+      ccForBuild  cxxForBuild  rustBuildPlatform   rustBuildPlatformSpec
+      ccForHost   cxxForHost   rustHostPlatform    rustHostPlatformSpec
+      ccForTarget cxxForTarget 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 targetPackages works, in
+    # situations where targetPackages is irrelevant
+    # targetPackages.stdenv.cc is often simply wrong.  We must omit
+    # the following lines when rustTargetPlatform collides with
+    # rustHostPlatform.
+    + lib.optionalString (rustTargetPlatform != rustHostPlatform) ''
+      "CC_${toRustTargetForUseInEnvVars stdenv.targetPlatform}=${ccForTarget}" \
+      "CXX_${toRustTargetForUseInEnvVars stdenv.targetPlatform}=${cxxForTarget}" \
+      "CARGO_TARGET_${toRustTargetForUseInEnvVars stdenv.targetPlatform}_LINKER=${ccForTarget}" \
+    '' + ''
+      "CC_${toRustTargetForUseInEnvVars stdenv.hostPlatform}=${ccForHost}" \
+      "CXX_${toRustTargetForUseInEnvVars stdenv.hostPlatform}=${cxxForHost}" \
+      "CARGO_TARGET_${toRustTargetForUseInEnvVars stdenv.hostPlatform}_LINKER=${ccForHost}" \
+    '' + ''
+      "CC_${toRustTargetForUseInEnvVars stdenv.buildPlatform}=${ccForBuild}" \
+      "CXX_${toRustTargetForUseInEnvVars stdenv.buildPlatform}=${cxxForBuild}" \
+      "CARGO_TARGET_${toRustTargetForUseInEnvVars stdenv.buildPlatform}_LINKER=${ccForBuild}" \
+      "CARGO_BUILD_TARGET=${rustBuildPlatform}" \
+      "HOST_CC=${buildPackages.stdenv.cc}/bin/cc" \
+      "HOST_CXX=${buildPackages.stdenv.cc}/bin/c++" \
+    '';
+  };
 }

pkgs/development/compilers/rust/1_72.nix

@@ -11,6 +11,7 @@
 
 { stdenv, lib
 , buildPackages
+, targetPackages
 , newScope, callPackage
 , CoreFoundation, Security, SystemConfiguration
 , pkgsBuildTarget, pkgsBuildBuild, pkgsBuildHost

pkgs/development/compilers/rust/default.nix

@@ -13,6 +13,7 @@
 }:
 { stdenv, lib
 , buildPackages
+, targetPackages
 , newScope, callPackage
 , CoreFoundation, Security, SystemConfiguration
 , pkgsBuildBuild
@@ -21,15 +22,15 @@
 
 let
   # Use `import` to make sure no packages sneak in here.
-  lib' = import ../../../build-support/rust/lib { inherit lib; };
+  lib' = import ../../../build-support/rust/lib { inherit lib stdenv buildPackages targetPackages; };
   # Allow faster cross compiler generation by reusing Build artifacts
   fastCross = (stdenv.buildPlatform == stdenv.hostPlatform) && (stdenv.hostPlatform != stdenv.targetPlatform);
 in
 {
   lib = lib';
 
   # Backwards compat before `lib` was factored out.
-  inherit (lib') toTargetArch toTargetOs toRustTarget toRustTargetSpec IsNoStdTarget;
+  inherit (lib') toTargetArch toTargetOs toRustTarget toRustTargetSpec IsNoStdTarget toRustTargetForUseInEnvVars envVars;
 
   # This just contains tools for now. But it would conceivably contain
   # libraries too, say if we picked some default/recommended versions to build

pkgs/development/libraries/libdovi/default.nix

@@ -28,19 +28,19 @@ rustPlatform.buildRustPackage rec {
 
   buildPhase = ''
     runHook preBuild
-    cargo cbuild -j $NIX_BUILD_CORES --release --frozen --prefix=${placeholder "out"} --target ${rustTargetPlatformSpec}
+    ${rust.envVars.setEnv} cargo cbuild -j $NIX_BUILD_CORES --release --frozen --prefix=${placeholder "out"} --target ${rustTargetPlatformSpec}
     runHook postBuild
   '';
 
   installPhase = ''
     runHook preInstall
-    cargo cinstall -j $NIX_BUILD_CORES --release --frozen --prefix=${placeholder "out"} --target ${rustTargetPlatformSpec}
+    ${rust.envVars.setEnv} cargo cinstall -j $NIX_BUILD_CORES --release --frozen --prefix=${placeholder "out"} --target ${rustTargetPlatformSpec}
     runHook postInstall
   '';
 
   checkPhase = ''
     runHook preCheck
-    cargo ctest -j $NIX_BUILD_CORES --release --frozen --prefix=${placeholder "out"} --target ${rustTargetPlatformSpec}
+    ${rust.envVars.setEnv} cargo ctest -j $NIX_BUILD_CORES --release --frozen --prefix=${placeholder "out"} --target ${rustTargetPlatformSpec}
     runHook postCheck
   '';
 

pkgs/development/libraries/libimagequant/default.nix

@@ -26,13 +26,13 @@ rustPlatform.buildRustPackage rec {
 
   postBuild = ''
     pushd imagequant-sys
-    cargo cbuild --release --frozen --prefix=${placeholder "out"} --target ${rustTargetPlatformSpec}
+    ${rust.envVars.setEnv} cargo cbuild --release --frozen --prefix=${placeholder "out"} --target ${rustTargetPlatformSpec}
     popd
   '';
 
   postInstall = ''
     pushd imagequant-sys
-    cargo cinstall --release --frozen --prefix=${placeholder "out"} --target ${rustTargetPlatformSpec}
+    ${rust.envVars.setEnv} cargo cinstall --release --frozen --prefix=${placeholder "out"} --target ${rustTargetPlatformSpec}
     popd
   '';
 

pkgs/tools/video/rav1e/default.nix

@@ -16,23 +16,6 @@
 let
   rustTargetPlatformSpec = rust.toRustTargetSpec stdenv.hostPlatform;
 
-  # TODO: if another package starts using cargo-c (seems likely),
-  # factor this out into a makeCargoChook expression in
-  # pkgs/build-support/rust/hooks/default.nix
-  ccForBuild = "${buildPackages.stdenv.cc}/bin/${buildPackages.stdenv.cc.targetPrefix}cc";
-  cxxForBuild = "${buildPackages.stdenv.cc}/bin/${buildPackages.stdenv.cc.targetPrefix}c++";
-  ccForHost = "${stdenv.cc}/bin/${stdenv.cc.targetPrefix}cc";
-  cxxForHost = "${stdenv.cc}/bin/${stdenv.cc.targetPrefix}c++";
-  rustBuildPlatform = rust.toRustTarget stdenv.buildPlatform;
-  rustTargetPlatform = rust.toRustTarget stdenv.hostPlatform;
-  setEnvVars = ''
-    env \
-      "CC_${rustBuildPlatform}"="${ccForBuild}" \
-      "CXX_${rustBuildPlatform}"="${cxxForBuild}" \
-      "CC_${rustTargetPlatform}"="${ccForHost}" \
-      "CXX_${rustTargetPlatform}"="${cxxForHost}" \
-  '';
-
 in rustPlatform.buildRustPackage rec {
   pname = "rav1e";
   version = "0.6.6";
@@ -64,13 +47,11 @@ in rustPlatform.buildRustPackage rec {
   checkType = "debug";
 
   postBuild =  ''
-    ${setEnvVars} \
-    cargo cbuild --release --frozen --prefix=${placeholder "out"} --target ${rustTargetPlatformSpec}
+    ${rust.envVars.setEnv} cargo cbuild --release --frozen --prefix=${placeholder "out"} --target ${rustTargetPlatformSpec}
   '';
 
   postInstall = ''
-    ${setEnvVars} \
-    cargo cinstall --release --frozen --prefix=${placeholder "out"} --target ${rustTargetPlatformSpec}
+    ${rust.envVars.setEnv} cargo cinstall --release --frozen --prefix=${placeholder "out"} --target ${rustTargetPlatformSpec}
   '';
 
   meta = with lib; {