From 9157ca6c0d8b883d391ecbb977c67571c8430e2f Mon Sep 17 00:00:00 2001
From: Michael Bryniarski <michael.bryniarski@gmail.com>
Date: Wed, 30 Sep 2026 20:06:24 -0700
Subject: [PATCH] ktx-tools: fix build with GCC 16

GCC 16 defaults to gnu++20, which 4.4.2's fmt usage does not compile
under. Pin C++17 until 5.0.0 is released. See
https://github.com/KhronosGroup/KTX-Software/issues/1172.

Assisted-by: Claude Code (Claude Opus 5.5)
---
 pkgs/by-name/kt/ktx-tools/package.nix | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/pkgs/by-name/kt/ktx-tools/package.nix b/pkgs/by-name/kt/ktx-tools/package.nix
index b3bc46692173..f6f686875c23 100644
--- a/pkgs/by-name/kt/ktx-tools/package.nix
+++ b/pkgs/by-name/kt/ktx-tools/package.nix
@@ -29,7 +29,12 @@ stdenv.mkDerivation (finalAttrs: {
 
   cmakeBuildType = "RelWithDebInfo";
 
-  cmakeFlags = [ "-DKTX_FEATURE_DOC=ON" ];
+  cmakeFlags = [
+    "-DKTX_FEATURE_DOC=ON"
+    # 4.4.x does not build with GCC 16's default of gnu++20; fixed upstream in 5.0.0
+    # https://github.com/KhronosGroup/KTX-Software/issues/1172
+    (lib.cmakeFeature "CMAKE_CXX_STANDARD" "17")
+  ];
 
   postPatch = ''
     patchShebangs .