From c0330b746600bfd91dbacb88837da5a16f947ba5 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <aaronGokaslan@gmail.com>
Date: Wed, 29 Jul 2026 11:08:57 -0700
Subject: [PATCH] Do not optin into CPP modules without SCAN_DEPS on Clang
 (#4867)

---
 CMakeLists.txt | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3b317942..6887839a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -65,7 +65,8 @@ if (CMAKE_VERSION VERSION_GREATER_EQUAL 3.28 AND CMAKE_CXX_STANDARD
       if ((CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION
                                                     GREATER_EQUAL 15)
           OR (CMAKE_CXX_COMPILER_ID STREQUAL "Clang"
-              AND CMAKE_CXX_COMPILER_VERSION GREATER_EQUAL 16)
+              AND CMAKE_CXX_COMPILER_VERSION GREATER_EQUAL 16
+              AND CMAKE_CXX_COMPILER_CLANG_SCAN_DEPS)
           OR (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC" AND MSVC_VERSION
                                                         GREATER_EQUAL 1934))
         set(FMT_USE_CMAKE_MODULES TRUE)