From 51755b0c00881bfe1602db0eb689efd2c66bcc20 Mon Sep 17 00:00:00 2001
From: Randy Eckenrode <randy@largeandhighquality.com>
Date: Sun, 29 Sep 2024 13:54:47 -0400
Subject: [PATCH] {bintools,cc}-wrapper: use a fallback SDK when
 `DEVELOPER_DIR` is not set

It is unusual to invoke a wrapped compiler without setting
`DEVELOPER_DIR`, but it can happen when a user adds a compiler to their
installed packages or when a package intentionally invokes the compiler
without an environment (such as the GHC binary packages).
---
 .../bintools-wrapper/add-darwin-ldflags-before.sh             | 2 +-
 pkgs/build-support/bintools-wrapper/default.nix               | 4 ++++
 pkgs/build-support/cc-wrapper/add-flags.sh                    | 2 +-
 pkgs/build-support/cc-wrapper/default.nix                     | 4 ++++
 4 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/pkgs/build-support/bintools-wrapper/add-darwin-ldflags-before.sh b/pkgs/build-support/bintools-wrapper/add-darwin-ldflags-before.sh
index afcfce8ea9d5..79f0546403f7 100644
--- a/pkgs/build-support/bintools-wrapper/add-darwin-ldflags-before.sh
+++ b/pkgs/build-support/bintools-wrapper/add-darwin-ldflags-before.sh
@@ -84,7 +84,7 @@ 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=${DEVELOPER_DIR_@suffixSalt@}
+DEVELOPER_DIR=${DEVELOPER_DIR_@suffixSalt@:-@fallback_sdk@}
 
 # Darwin looks for frameworks in the SDK located at `DEVELOPER_DIR`.
 extraBefore+=("-F$DEVELOPER_DIR/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/System/Library/Frameworks")
diff --git a/pkgs/build-support/bintools-wrapper/default.nix b/pkgs/build-support/bintools-wrapper/default.nix
index b64e97345ab5..4a6457350102 100644
--- a/pkgs/build-support/bintools-wrapper/default.nix
+++ b/pkgs/build-support/bintools-wrapper/default.nix
@@ -10,6 +10,7 @@
 , stdenvNoCC
 , runtimeShell
 , bintools ? null, libc ? null, coreutils ? null, gnugrep ? null
+, apple-sdk ? null
 , netbsd ? null
 , sharedLibraryLoader ?
   if libc == null then
@@ -412,6 +413,9 @@ 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.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;
   };
 
   meta =
diff --git a/pkgs/build-support/cc-wrapper/add-flags.sh b/pkgs/build-support/cc-wrapper/add-flags.sh
index 6683337b77b9..cd5396f45f8b 100644
--- a/pkgs/build-support/cc-wrapper/add-flags.sh
+++ b/pkgs/build-support/cc-wrapper/add-flags.sh
@@ -90,7 +90,7 @@ if [ "@darwinMinVersion@" ]; then
 
     # 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=${DEVELOPER_DIR_@suffixSalt@}
+    DEVELOPER_DIR=${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.
diff --git a/pkgs/build-support/cc-wrapper/default.nix b/pkgs/build-support/cc-wrapper/default.nix
index 01f91b408e38..ed55e37cb76a 100644
--- a/pkgs/build-support/cc-wrapper/default.nix
+++ b/pkgs/build-support/cc-wrapper/default.nix
@@ -10,6 +10,7 @@
 , stdenvNoCC
 , runtimeShell
 , cc ? null, libc ? null, bintools, coreutils ? null
+, apple-sdk ? null
 , zlib ? null
 , nativeTools, noLibc ? false, nativeLibc, nativePrefix ? ""
 , propagateDoc ? cc != null && cc ? man
@@ -749,6 +750,9 @@ stdenvNoCC.mkDerivation {
     inherit libc_bin libc_dev libc_lib;
     inherit darwinPlatformForCC darwinMinVersion darwinMinVersionVariable;
     default_hardening_flags_str = builtins.toString defaultHardeningFlags;
+  } // 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;
   };
 
   meta =