From 8684506269d29f129a28702a519467af8524ecb4 Mon Sep 17 00:00:00 2001
From: Andrew Davis <andrew.davis@ukaea.uk>
Date: Tue, 7 Jul 2026 15:58:19 +0100
Subject: [PATCH] This fixes compile isuees found with GCC 16.1.1 and FMT
 version (#4000)

Co-authored-by: Paul Romano <paul.k.romano@gmail.com>
---
 include/openmc/error.h       | 4 ++--
 src/distribution_spatial.cpp | 8 +++++---
 src/weight_windows.cpp       | 3 ++-
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/openmc/error.h b/include/openmc/error.h
index d73795aee..1f6e15f49 100644
--- a/include/openmc/error.h
+++ b/include/openmc/error.h
@@ -64,14 +64,14 @@ void write_message(
   int level, const std::string& message, const Params&... fmt_args)
 {
   if (settings::verbosity >= level) {
-    write_message(fmt::format(message, fmt_args...));
+    write_message(fmt::format(fmt::runtime(message), fmt_args...));
   }
 }
 
 template<typename... Params>
 void write_message(const std::string& message, const Params&... fmt_args)
 {
-  write_message(fmt::format(message, fmt_args...));
+  write_message(fmt::format(fmt::runtime(message), fmt_args...));
 }
 
 #ifdef OPENMC_MPI
diff --git a/src/distribution_spatial.cpp b/src/distribution_spatial.cpp
index ba8658f10..5a3452422 100644
--- a/src/distribution_spatial.cpp
+++ b/src/distribution_spatial.cpp
@@ -262,9 +262,11 @@ std::pair<Position, double> SphericalIndependent::sample(uint64_t* seed) const
 MeshSpatial::MeshSpatial(pugi::xml_node node)
 {
 
-  if (get_node_value(node, "type", true, true) != "mesh") {
-    fatal_error(fmt::format(
-      "Incorrect spatial type '{}' for a MeshSpatial distribution"));
+  auto spatial_type = get_node_value(node, "type", true, true);
+  if (spatial_type != "mesh") {
+    fatal_error(
+      fmt::format("Incorrect spatial type '{}' for a MeshSpatial distribution",
+        spatial_type));
   }
 
   // No in-tet distributions implemented, could include distributions for the
diff --git a/src/weight_windows.cpp b/src/weight_windows.cpp
index 39e46026c..0d268ce17 100644
--- a/src/weight_windows.cpp
+++ b/src/weight_windows.cpp
@@ -837,7 +837,8 @@ WeightWindowsGenerator::WeightWindowsGenerator(pugi::xml_node node)
       ratio_));
   if (ratio_ <= 1.0)
     fatal_error(fmt::format("Invalid weight window ratio '{}' (<= 1.0) "
-                            "specified for weight window generation"));
+                            "specified for weight window generation",
+      ratio_));
 
   // create a matching weight windows object
   auto wws = WeightWindows::create();