From 14c46fb16a6c431e3b011d101d4d19f51ff8ad27 Mon Sep 17 00:00:00 2001
From: Christoph Junghans <junghans@votca.org>
Date: Tue, 13 Dec 2022 18:29:18 -0700
Subject: FindHDF5: Find C component with only CXX compiler

For CXX-only projects it is sometimes useful to detect the C
component even with just a CXX compiler.

Fixes: #24241
---
 Modules/FindHDF5.cmake | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Modules/FindHDF5.cmake b/Modules/FindHDF5.cmake
index d662a7d..db03c54 100644
--- a/Modules/FindHDF5.cmake
+++ b/Modules/FindHDF5.cmake
@@ -222,6 +222,10 @@ function(_HDF5_test_regular_compiler_C success version is_parallel)
   if(NOT ${success} OR
      NOT EXISTS ${scratch_directory}/compiler_has_h5_c)
     set(test_file ${scratch_directory}/cmake_hdf5_test.c)
+    # CXX project without C enabled
+    if(CMAKE_CXX_COMPILER_LOADED AND NOT CMAKE_C_COMPILER_LOADED)
+      set(test_file ${scratch_directory}/cmake_hdf5_test.cpp)
+    endif()
     file(WRITE ${test_file}
       "#include <hdf5.h>\n"
       "const char* info_ver = \"INFO\" \":\" H5_VERSION;\n"
-- 
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