From c872acae63feb8b391f6919b94c2d2d06deb1a19 Mon Sep 17 00:00:00 2001
From: Allen Byrne <50328838+byrnHDF@users.noreply.github.com>
Date: Thu, 7 Mar 2024 11:27:56 -0600
Subject: New option for building with static CRT in Windows (#4062)

---
 config/cmake/HDFUseFortran.cmake         |  8 --------
 config/cmake/UserMacros/Windows_MT.cmake | 34 +++++---------------------------
 release_docs/INSTALL_CMake.txt           |  9 +++------
 release_docs/RELEASE.txt                 |  9 +++++++++
 4 files changed, 17 insertions(+), 43 deletions(-)

diff --git a/config/cmake/HDFUseFortran.cmake b/config/cmake/HDFUseFortran.cmake
index 392ea30..2d53a50 100644
--- a/config/cmake/HDFUseFortran.cmake
+++ b/config/cmake/HDFUseFortran.cmake
@@ -19,14 +19,6 @@ set (HDF_PREFIX "H5")
 include (CheckFortranSourceRuns)
 include (CheckFortranSourceCompiles)
 
-#-------------------------------------------------------------------------------
-#  Fix Fortran flags if we are compiling statically on Windows using
-#  Windows_MT.cmake from config/cmake/UserMacros
-#-------------------------------------------------------------------------------
-if (BUILD_STATIC_CRT_LIBS)
-  TARGET_STATIC_CRT_FLAGS ()
-endif ()
-
 #-----------------------------------------------------------------------------
 # Detect name mangling convention used between Fortran and C
 #-----------------------------------------------------------------------------
diff --git a/config/cmake/UserMacros/Windows_MT.cmake b/config/cmake/UserMacros/Windows_MT.cmake
index c8edbe4..351c991 100644
--- a/config/cmake/UserMacros/Windows_MT.cmake
+++ b/config/cmake/UserMacros/Windows_MT.cmake
@@ -20,34 +20,10 @@
 # INCLUDE(path_to_file/WINDOWS_MT.cmake)
 
 #-----------------------------------------------------------------------------
-# Option to Build with Static CRT libraries on Windows
-#-------------------------------------------------------------------------------
-macro (TARGET_STATIC_CRT_FLAGS)
-  if (MSVC AND NOT BUILD_SHARED_LIBS)
-    foreach (flag_var
-        CMAKE_C_FLAGS CMAKE_C_FLAGS_DEBUG CMAKE_C_FLAGS_RELEASE
-        CMAKE_C_FLAGS_MINSIZEREL CMAKE_C_FLAGS_RELWITHDEBINFO
-        CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE
-        CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO)
-      if (${flag_var} MATCHES "/MD")
-        string (REGEX REPLACE "/MD" "/MT" ${flag_var} "${${flag_var}}")
-      endif ()
-    endforeach ()
-    foreach (flag_var
-        CMAKE_Fortran_FLAGS CMAKE_Fortran_FLAGS_DEBUG CMAKE_Fortran_FLAGS_RELEASE
-        CMAKE_Fortran_FLAGS_MINSIZEREL CMAKE_Fortran_FLAGS_RELWITHDEBINFO)
-      if (${flag_var} MATCHES "/libs:dll")
-        string (REGEX REPLACE "/libs:dll" "/libs:static" ${flag_var} "${${flag_var}}")
-      endif ()
-    endforeach ()
-    set (WIN_COMPILE_FLAGS "")
-    set (WIN_LINK_FLAGS "/NODEFAULTLIB:MSVCRT")
-  endif ()
-endmacro ()
-
+# Option to Build with Static CRT libraries on Windows (USE WITH CAUTION!!!)
 #-----------------------------------------------------------------------------
-option (BUILD_STATIC_CRT_LIBS "Build With Static CRT Libraries" OFF)
-mark_as_advanced (BUILD_STATIC_CRT_LIBS)
-if (BUILD_STATIC_CRT_LIBS)
-  TARGET_STATIC_CRT_FLAGS ()
+option (HDF5_BUILD_STATIC_CRT_LIBS "Build With Static Windows CRT Libraries" OFF)
+mark_as_advanced (HDF5_BUILD_STATIC_CRT_LIBS)
+if (HDF5_BUILD_STATIC_CRT_LIBS)
+  set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
 endif ()
diff --git a/release_docs/INSTALL_CMake.txt b/release_docs/INSTALL_CMake.txt
index 392abf3..4d4af24 100644
--- a/release_docs/INSTALL_CMake.txt
+++ b/release_docs/INSTALL_CMake.txt
@@ -968,13 +968,10 @@ VII. User Defined Options for HDF5 Libraries with CMake
 ========================================================================
 
 Support for User Defined macros and options has been added. The file
-UserMacros.cmake has an example of the technique. In the folder,
-config/cmake/UserMacros, is an implementation for Windows Visual Studio
-users for linking libraries to the static CRT - Windows_MT.cmake.
+UserMacros.cmake has an example of the technique.
 
-Copy the contents of the file, both macro and option, into the
-UserMacros.cmake file. Then enable the option to the CMake configuration,
-build and test process.
+Replace the template code with your macro in the UserMacros.cmake file.
+Then enable the option to the CMake configuration, build and test process.
 
 
 ========================================================================
diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index 9ef3f45..25bcbbf 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -47,6 +47,15 @@ New Features
 
     Configuration:
     -------------
+    - New option for building with static CRT in Windows
+
+      The following option has been added:
+        HDF5_BUILD_STATIC_CRT_LIBS    "Build With Static Windows CRT Libraries"          OFF
+      Because our minimum CMake is 3.18, the macro to change runtime flags no longer
+      works as CMake changed the default behavior in CMake 3.15.
+
+      Fixes GitHub issue #3984
+
     - Added support for the new MSVC preprocessor
 
       Microsoft added support for a new, standards-conformant preprocessor
-- 
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