From 3f3907b5d18b7ecf8512dae4a929fae10788a4e7 Mon Sep 17 00:00:00 2001
From: Tony Wasserka <neobrain@users.noreply.github.com>
Date: Fri, 27 Jun 2025 15:43:22 +0200
Subject: [PATCH] Build: Add nix-based helpers to manage toolchains for
 FEXLinuxTests

The cmake_enable_flt.sh script will automatically install the required
cross-toolchains required to build FEXLinuxTests, and it will reconfigure
the current build folder appropriately.

For advanced uses, a shell can be opened by running `nix-shell FEXLinuxTests/shell.nix`,
which will make the toolchain available via environment variables.
---
 Data/nix/FEXLinuxTests/shell.nix | 35 ++++++++++++++++++++++++++++++++
 Data/nix/cmake_enable_flt.sh     | 17 ++++++++++++++++
 2 files changed, 52 insertions(+)
 create mode 100644 Data/nix/FEXLinuxTests/shell.nix
 create mode 100755 Data/nix/cmake_enable_flt.sh

diff --git a/Data/nix/FEXLinuxTests/shell.nix b/Data/nix/FEXLinuxTests/shell.nix
new file mode 100644
index 000000000..7cbf8c195
--- /dev/null
+++ b/Data/nix/FEXLinuxTests/shell.nix
@@ -0,0 +1,35 @@
+{ pkgs ? import <nixpkgs> { } }:
+
+let
+  pkgsCross32 = pkgs.pkgsCross.gnu32;
+  pkgsCross64 = pkgs.pkgsCross.gnu64;
+
+  gcc32 = pkgs.writeText "toolchain_nix_gcc_x86_32.txt" ''
+    set(CMAKE_SYSTEM_PROCESSOR i686)
+    set(CMAKE_C_COMPILER ${pkgsCross32.buildPackages.gcc}/bin/i686-unknown-linux-gnu-gcc)
+    set(CMAKE_CXX_COMPILER ${pkgsCross32.buildPackages.gcc}/bin/i686-unknown-linux-gnu-g++)
+  '';
+
+  gcc64 = pkgs.writeText "toolchain_nix_gcc_x86_64.txt" ''
+    set(CMAKE_SYSTEM_PROCESSOR x86_64)
+    set(CMAKE_C_COMPILER ${pkgsCross64.buildPackages.gcc}/bin/x86_64-unknown-linux-gnu-gcc)
+    set(CMAKE_CXX_COMPILER ${pkgsCross64.buildPackages.gcc}/bin/x86_64-unknown-linux-gnu-g++)
+  '';
+in
+pkgs.mkShell {
+  buildInputs = [
+    pkgsCross64.buildPackages.clang
+    pkgsCross32.buildPackages.clang
+  ];
+
+  shellHook = ''
+    if [[ $- == *i* ]]; then
+      echo "toolchain32: ${gcc32}"
+      echo "toolchain64: ${gcc64}"
+      echo ""
+      echo "Use \$FEX_CMAKE_TOOLCHAINS to configure CMake."
+    fi
+  '';
+
+  FEX_CMAKE_TOOLCHAINS = "-DX86_32_TOOLCHAIN_FILE=${gcc32} -DX86_64_TOOLCHAIN_FILE=${gcc64}";
+}
diff --git a/Data/nix/cmake_enable_flt.sh b/Data/nix/cmake_enable_flt.sh
new file mode 100755
index 000000000..22077e657
--- /dev/null
+++ b/Data/nix/cmake_enable_flt.sh
@@ -0,0 +1,17 @@
+#! /usr/bin/env nix-shell
+#! nix-shell -i bash FEXLinuxTests/shell.nix
+
+# Helper script to configure CMake for building FEXLinuxTests.
+# Nix is used to install and manage the required cross-toolchains.
+
+if [ ! -f CMakeCache.txt ]
+then
+  echo "Must be run from a pre-configured CMake build folder"
+  exit 1
+fi
+
+# Remove previous build to ensure the new toolchain is applied
+rm -rf unittests/FEXLinuxTests
+
+set -o xtrace
+cmake . $FEX_CMAKE_TOOLCHAINS -DBUILD_TESTS=ON -DBUILD_FEX_LINUX_TESTS=ON