From f42e2b00c9559b9335bf744b12a6de9534c3ca9a Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Sat, 7 Feb 2026 12:45:34 -0600
Subject: [PATCH] fix: Dynamically find Erlang erts include directory

Find the erts include path dynamically instead of relying on
erlang.version which may not match the actual erts version.
This fixes 'erl_nif.h' file not found error.
---
 nix/c-nif.nix | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/nix/c-nif.nix b/nix/c-nif.nix
index a0c502ce..bf64d982 100644
--- a/nix/c-nif.nix
+++ b/nix/c-nif.nix
@@ -26,15 +26,13 @@ stdenv.mkDerivation {
     erlang
   ];
 
-  # Set Erlang include path for NIF headers
-  preBuild = ''
-    export ERL_INCLUDE_PATH="${erlang}/lib/erlang/erts-${erlang.version}/include"
-  '';
-
   # Build using the existing Makefile
   buildPhase = ''
     runHook preBuild
 
+    # Find the actual erts include directory
+    export ERL_INCLUDE_PATH=$(find ${erlang}/lib/erlang -type d -name "erts-*" | head -1)/include
+
     cd c_src
     make -j$NIX_BUILD_CORES