From 58376e1f1d079ac0f41515ce26801d442f691e61 Mon Sep 17 00:00:00 2001
From: Guilhem Saurel <guilhem.saurel@laas.fr>
Date: Wed, 6 Aug 2025 17:24:58 +0200
Subject: [PATCH] eigen: fix bdcsvd

---
 pkgs/by-name/ei/eigen/package.nix | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/pkgs/by-name/ei/eigen/package.nix b/pkgs/by-name/ei/eigen/package.nix
index eaa298848184..898f83d2d136 100644
--- a/pkgs/by-name/ei/eigen/package.nix
+++ b/pkgs/by-name/ei/eigen/package.nix
@@ -20,6 +20,14 @@ stdenv.mkDerivation {
     ./include-dir.patch
   ];
 
+  # ref. https://gitlab.com/libeigen/eigen/-/merge_requests/977
+  # This was merged upstream and can be removed on next release
+  postPatch = ''
+    substituteInPlace Eigen/src/SVD/BDCSVD.h --replace-fail \
+      "if (l == 0) {" \
+      "if (i >= k && l == 0) {"
+  '';
+
   nativeBuildInputs = [ cmake ];
 
   meta = with lib; {