{bintools-wrapper,cc-wrapper}: factor out Darwin SDK logic

This reduces code duplication, makes the SDK variables available
earlier in the wrappers, and makes the behaviour between the two
wrappers more consistent.

pkgs/build-support/bintools-wrapper/add-darwin-ldflags-before.sh

@@ -79,9 +79,3 @@ if [ ! "$havePlatformVersionFlag" ]; then
         extraBefore+=(-@darwinPlatform@_version_min "${@darwinMinVersionVariable@_@suffixSalt@:-@darwinMinVersion@}")
     fi
 fi
-
-mangleVarSingle DEVELOPER_DIR ${role_suffixes[@]+"${role_suffixes[@]}"}
-
-# Allow wrapped bintools to do something useful when no `DEVELOPER_DIR` is set, which can happen when
-# the compiler is run outside of a stdenv or intentionally in an environment with no environment variables set.
-DEVELOPER_DIR=${DEVELOPER_DIR_@suffixSalt@:-@fallback_sdk@}

pkgs/build-support/bintools-wrapper/default.nix

@@ -372,24 +372,15 @@ stdenvNoCC.mkDerivation {
       substituteAll ${./add-flags.sh} $out/nix-support/add-flags.sh
       substituteAll ${./add-hardening.sh} $out/nix-support/add-hardening.sh
       substituteAll ${../wrapper-common/utils.bash} $out/nix-support/utils.bash
+      substituteAll ${../wrapper-common/darwin-sdk-setup.bash} $out/nix-support/darwin-sdk-setup.bash
     ''
 
     ###
     ### Ensure consistent LC_VERSION_MIN_MACOSX
     ###
-    + optionalString targetPlatform.isDarwin (
-      let
-        inherit (targetPlatform)
-          darwinPlatform darwinSdkVersion
-          darwinMinVersion darwinMinVersionVariable;
-      in ''
-        export darwinPlatform=${darwinPlatform}
-        export darwinMinVersion=${darwinMinVersion}
-        export darwinSdkVersion=${darwinSdkVersion}
-        export darwinMinVersionVariable=${darwinMinVersionVariable}
-        substituteAll ${./add-darwin-ldflags-before.sh} $out/nix-support/add-local-ldflags-before.sh
-      ''
-    )
+    + optionalString targetPlatform.isDarwin ''
+      substituteAll ${./add-darwin-ldflags-before.sh} $out/nix-support/add-local-ldflags-before.sh
+    ''
 
     ##
     ## Extra custom steps
@@ -407,6 +398,11 @@ stdenvNoCC.mkDerivation {
     inherit dynamicLinker targetPrefix suffixSalt coreutils_bin;
     inherit bintools_bin libc_bin libc_dev libc_lib;
     default_hardening_flags_str = builtins.toString defaultHardeningFlags;
+  } // lib.mapAttrs (_: lib.optionalString targetPlatform.isDarwin) {
+    # These will become empty strings when not targeting Darwin.
+    inherit (targetPlatform)
+      darwinPlatform darwinSdkVersion
+      darwinMinVersion darwinMinVersionVariable;
   } // lib.optionalAttrs (apple-sdk != null && stdenvNoCC.targetPlatform.isDarwin) {
     # Wrapped compilers should do something useful even when no SDK is provided at `DEVELOPER_DIR`.
     fallback_sdk = apple-sdk.__spliced.buildTarget or apple-sdk;

pkgs/build-support/bintools-wrapper/ld-wrapper.sh

@@ -16,6 +16,8 @@ fi
 
 source @out@/nix-support/utils.bash
 
+source @out@/nix-support/darwin-sdk-setup.bash
+
 if [ -z "${NIX_BINTOOLS_WRAPPER_FLAGS_SET_@suffixSalt@:-}" ]; then
     source @out@/nix-support/add-flags.sh
 fi

pkgs/build-support/cc-wrapper/add-flags.sh

@@ -78,23 +78,12 @@ if [ -e @out@/nix-support/cc-cflags-before ]; then
     NIX_CFLAGS_COMPILE_BEFORE_@suffixSalt@="$(< @out@/nix-support/cc-cflags-before) $NIX_CFLAGS_COMPILE_BEFORE_@suffixSalt@"
 fi
 
-# Only add darwin min version flag and set up `DEVELOPER_DIR` if a default darwin min version is set,
+# Only add darwin min version flag if a default darwin min version is set,
 # which is a signal that we're targetting darwin.
 if [ "@darwinMinVersion@" ]; then
     mangleVarSingle @darwinMinVersionVariable@ ${role_suffixes[@]+"${role_suffixes[@]}"}
 
     NIX_CFLAGS_COMPILE_BEFORE_@suffixSalt@="-m@darwinPlatformForCC@-version-min=${@darwinMinVersionVariable@_@suffixSalt@:-@darwinMinVersion@} $NIX_CFLAGS_COMPILE_BEFORE_@suffixSalt@"
-
-    # `DEVELOPER_DIR` is used to dynamically locate libSystem (and the SDK frameworks) based on the SDK at that path.
-    mangleVarSingle DEVELOPER_DIR ${role_suffixes[@]+"${role_suffixes[@]}"}
-
-    # Allow wrapped compilers to do something useful when no `DEVELOPER_DIR` is set, which can happen when
-    # the compiler is run outside of a stdenv or intentionally in an environment with no environment variables set.
-    DEVELOPER_DIR=${DEVELOPER_DIR_@suffixSalt@:-@fallback_sdk@}
-
-    # xcbuild needs `SDKROOT` to be the name of the SDK, which it sets in its own wrapper,
-    # but compilers expect it to point to the absolute path.
-    SDKROOT="$DEVELOPER_DIR/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk"
 fi
 
 # That way forked processes will not extend these environment variables again.

pkgs/build-support/cc-wrapper/cc-wrapper.sh

@@ -17,6 +17,8 @@ fi
 
 source @out@/nix-support/utils.bash
 
+source @out@/nix-support/darwin-sdk-setup.bash
+
 
 # Parse command line options and set several variables.
 # For instance, figure out if linker flags should be passed.

pkgs/build-support/cc-wrapper/default.nix

@@ -284,13 +284,6 @@ let
     if (targetPlatform.darwinPlatform == "macos" && isGNU) then "macosx"
     else targetPlatform.darwinPlatform
   );
-
-  darwinMinVersion = optionalString targetPlatform.isDarwin (
-    targetPlatform.darwinMinVersion
-  );
-
-  darwinMinVersionVariable = optionalString targetPlatform.isDarwin
-    targetPlatform.darwinMinVersionVariable;
 in
 
 assert includeFortifyHeaders' -> fortify-headers != null;
@@ -707,6 +700,7 @@ stdenvNoCC.mkDerivation {
       substituteAll ${./add-flags.sh} $out/nix-support/add-flags.sh
       substituteAll ${./add-hardening.sh} $out/nix-support/add-hardening.sh
       substituteAll ${../wrapper-common/utils.bash} $out/nix-support/utils.bash
+      substituteAll ${../wrapper-common/darwin-sdk-setup.bash} $out/nix-support/darwin-sdk-setup.bash
     ''
 
     + optionalString cc.langAda or false ''
@@ -751,8 +745,11 @@ stdenvNoCC.mkDerivation {
     wrapperName = "CC_WRAPPER";
     inherit suffixSalt coreutils_bin bintools;
     inherit libc_bin libc_dev libc_lib;
-    inherit darwinPlatformForCC darwinMinVersion darwinMinVersionVariable;
+    inherit darwinPlatformForCC;
     default_hardening_flags_str = builtins.toString defaultHardeningFlags;
+  } // lib.mapAttrs (_: lib.optionalString targetPlatform.isDarwin) {
+    # These will become empty strings when not targeting Darwin.
+    inherit (targetPlatform) darwinMinVersion darwinMinVersionVariable;
   } // lib.optionalAttrs (apple-sdk != null && stdenvNoCC.targetPlatform.isDarwin) {
     # Wrapped compilers should do something useful even when no SDK is provided at `DEVELOPER_DIR`.
     fallback_sdk = apple-sdk.__spliced.buildTarget or apple-sdk;

pkgs/build-support/wrapper-common/darwin-sdk-setup.bash

@@ -0,0 +1,16 @@
+accumulateRoles
+
+# Only set up `DEVELOPER_DIR` if a default darwin min version is set,
+# which is a signal that we're targetting darwin.
+if [[ "@darwinMinVersion@" ]]; then
+    # `DEVELOPER_DIR` is used to dynamically locate libSystem (and the SDK frameworks) based on the SDK at that path.
+    mangleVarSingle DEVELOPER_DIR ${role_suffixes[@]+"${role_suffixes[@]}"}
+
+    # Allow wrapped compilers to do something useful when no `DEVELOPER_DIR` is set, which can happen when
+    # the compiler is run outside of a stdenv or intentionally in an environment with no environment variables set.
+    DEVELOPER_DIR=${DEVELOPER_DIR_@suffixSalt@:-@fallback_sdk@}
+
+    # xcbuild needs `SDKROOT` to be the name of the SDK, which it sets in its own wrapper,
+    # but compilers expect it to point to the absolute path.
+    SDKROOT="$DEVELOPER_DIR/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk"
+fi