From ee727667975ccac39a74386ab7c55984165220b6 Mon Sep 17 00:00:00 2001
From: Thomas Beutlich <modelica@tbeu.de>
Date: Wed, 29 Jan 2025 21:16:29 +0100
Subject: [PATCH] refs #52: Test and fix MSVC linker error on duplicated
 symbols

---
 ExternData/Resources/BuildProjects/CMake/test.cmake |  4 ++++
 ExternData/Resources/Include/msvc_compatibility.h   |  4 ++--
 ExternData/Resources/Test/Test_Linkage.c            |  9 +++++++++
 ExternData/Resources/Test/Test_Linkage.cc           | 10 ++++++++++
 4 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 ExternData/Resources/Test/Test_Linkage.c
 create mode 100644 ExternData/Resources/Test/Test_Linkage.cc

diff --git a/ExternData/Resources/BuildProjects/CMake/test.cmake b/ExternData/Resources/BuildProjects/CMake/test.cmake
index 2363c23..50c4640 100644
--- a/ExternData/Resources/BuildProjects/CMake/test.cmake
+++ b/ExternData/Resources/BuildProjects/CMake/test.cmake
@@ -46,6 +46,8 @@ if(EXISTS "${ED_TEST_DIR}")
   foreach(TEST ${ED_TESTS})
     add_executable(${TEST}
       "${ED_TEST_DIR}/${TEST}.cc"
+      "${ED_TEST_DIR}/Test_Linkage.cc"
+      "${ED_TEST_DIR}/Test_Linkage.c"
       "${ED_TEST_DIR}/Constants.h"
     )
     target_compile_features(${TEST} PRIVATE cxx_std_17)
@@ -73,6 +75,8 @@ if(EXISTS "${ED_TEST_DIR}")
     )
     if(UNIX)
       list(APPEND ED_ALL_LIBS m)
+    elseif(MSVC)
+      target_link_options(${TEST} PRIVATE "/FORCE:MULTIPLE")
     endif()
     target_link_libraries(${TEST} PRIVATE ${ED_ALL_LIBS})
 
diff --git a/ExternData/Resources/Include/msvc_compatibility.h b/ExternData/Resources/Include/msvc_compatibility.h
index 777f2c7..2538436 100644
--- a/ExternData/Resources/Include/msvc_compatibility.h
+++ b/ExternData/Resources/Include/msvc_compatibility.h
@@ -23,14 +23,14 @@
 extern "C" {
 #endif
 
-extern long timezone = 0;
+__declspec(selectany) extern long timezone = 0;
 
 #if defined(G_HAS_CONSTRUCTORS)
 #ifdef G_DEFINE_CONSTRUCTOR_NEEDS_PRAGMA
 #pragma G_DEFINE_CONSTRUCTOR_PRAGMA_ARGS(Timezone_initialize)
 #endif
 G_DEFINE_CONSTRUCTOR(Timezone_initialize)
-static void Timezone_initialize(void) {
+static inline void Timezone_initialize(void) {
 	_get_timezone(&timezone);
 }
 #endif
diff --git a/ExternData/Resources/Test/Test_Linkage.c b/ExternData/Resources/Test/Test_Linkage.c
new file mode 100644
index 0000000..d2afe32
--- /dev/null
+++ b/ExternData/Resources/Test/Test_Linkage.c
@@ -0,0 +1,9 @@
+/* Test_Linkage.c
+ *
+ * Copyright (C) 2015-2025, Thomas Beutlich
+ * All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "../Include/msvc_compatibility.h"
diff --git a/ExternData/Resources/Test/Test_Linkage.cc b/ExternData/Resources/Test/Test_Linkage.cc
new file mode 100644
index 0000000..c538523
--- /dev/null
+++ b/ExternData/Resources/Test/Test_Linkage.cc
@@ -0,0 +1,10 @@
+/* Test_Linkage.cc
+ *
+ * Copyright (C) 2015-2025, Thomas Beutlich
+ * All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "../Include/msvc_compatibility.h"
+#include "Constants.h"