From 1e48bc82157a8fe24b0ba3a635056c07d5caad49 Mon Sep 17 00:00:00 2001
From: Karolis Stasaitis <contact@carlossless.io>
Date: Wed, 30 Sep 2026 12:58:48 +0200
Subject: [PATCH] systemc: default SC_CPLUSPLUS to C++17 in installed headers

---
 pkgs/by-name/sy/systemc/package.nix | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/pkgs/by-name/sy/systemc/package.nix b/pkgs/by-name/sy/systemc/package.nix
index 6bb45b8d99bb..cb53e6833071 100644
--- a/pkgs/by-name/sy/systemc/package.nix
+++ b/pkgs/by-name/sy/systemc/package.nix
@@ -16,6 +16,12 @@ stdenv.mkDerivation (finalAttrs: {
     hash = "sha256-v/PcQu0m/7zyx2TtpZrLFbHtknahgVCkzcRi3lgrRGw=";
   };
 
+  # consumers must see the SC_CPLUSPLUS the library was built with, otherwise it follows their own -std and fails to link
+  postPatch = ''
+    substituteInPlace src/sysc/kernel/sc_cmnhdr.h \
+      --replace-fail '#  define SC_CPLUSPLUS SC_CPLUSPLUS_AUTO_' '#  define SC_CPLUSPLUS 201703L'
+  '';
+
   nativeBuildInputs = [ cmake ];
 
   cmakeFlags = [