From 1c9ed10d9f4e3ae74d734b73fd4dd7e86c3ffb30 Mon Sep 17 00:00:00 2001
From: Mahder Gebremedhin <mahge@users.noreply.github.com>
Date: Thu, 31 Aug 2023 14:29:52 +0200
Subject: [PATCH] Improve omqwt compilation. Fix possbile errors. (#11106)

  - Define `QWT_DL` and `QWT_MAKEDLL` accordingly for all Windows compilations
    not just for `MSVC`.

  - Fix const qualifiers in `omc_msvc.c`. Removing const qualifiers on
    return values seems to be considered an error by `MinGW clang-11`.
    Possibly a warning on others.
---
 OMCompiler/SimulationRuntime/c/util/omc_msvc.c |  4 ++--
 OMCompiler/SimulationRuntime/c/util/omc_msvc.h |  4 ++--
 OMPlot/qwt/src/CMakeLists.txt                  | 14 ++++++++------
 3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/OMCompiler/SimulationRuntime/c/util/omc_msvc.c b/OMCompiler/SimulationRuntime/c/util/omc_msvc.c
index 6a138ee4abe..b33a7e8f401 100644
--- a/OMCompiler/SimulationRuntime/c/util/omc_msvc.c
+++ b/OMCompiler/SimulationRuntime/c/util/omc_msvc.c
@@ -258,7 +258,7 @@ static const char* GetLastErrorAsString()
   return str;
 }
 
-char* omc_dlerror()
+const char* omc_dlerror()
 {
   return GetLastErrorAsString();
 }
@@ -277,7 +277,7 @@ void* dlopen(const char *filename, int flag) {
   return omc_dlopen(filename, flag);
 }
 
-char* dlerror() {
+const char* dlerror() {
   return omc_dlerror();
 }
 
diff --git a/OMCompiler/SimulationRuntime/c/util/omc_msvc.h b/OMCompiler/SimulationRuntime/c/util/omc_msvc.h
index 0034a425981..105c5cea3be 100644
--- a/OMCompiler/SimulationRuntime/c/util/omc_msvc.h
+++ b/OMCompiler/SimulationRuntime/c/util/omc_msvc.h
@@ -159,13 +159,13 @@ typedef struct {
 
 char* mkdtemp(char *tpl);
 void* omc_dlopen(const char *filename, int flag);
-char* omc_dlerror();
+const char* omc_dlerror();
 void* omc_dlsym(void *handle, const char *symbol);
 int omc_dlclose(void *handle);
 int omc_dladdr(void *addr, Dl_info *info);
 
 void* dlopen(const char *filename, int flag);
-char* dlerror();
+const char* dlerror();
 void* dlsym(void *handle, const char *symbol);
 int dlclose(void *handle);
 int dladdr(void *addr, Dl_info *info);
diff --git a/OMPlot/qwt/src/CMakeLists.txt b/OMPlot/qwt/src/CMakeLists.txt
index 0161612817e..bdcda2ed5e8 100644
--- a/OMPlot/qwt/src/CMakeLists.txt
+++ b/OMPlot/qwt/src/CMakeLists.txt
@@ -216,12 +216,14 @@ endif ()
 
 add_library(omqwt SHARED ${QWT_HEADERS} ${QWT_SOURCES})
 
-target_compile_definitions(omqwt
-	PUBLIC
-		$<$<BOOL:MSVC>:QWT_DLL>
-	PRIVATE
-		$<$<BOOL:MSVC>:QWT_MAKEDLL>
-)
+if(WIN32)
+  # define QWT_DLL so the headers add the dll export/import specifiers .
+  target_compile_definitions(omqwt PUBLIC QWT_DLL)
+  # When compiling omqwt itself, define QWT_MAKEDLL so the headers export the functions.
+  # Target that link to omqwt will not fet this define (private) which means they will
+  # dllimport the functions. See src/qwt_global.h:27-35
+  target_compile_definitions(omqwt PRIVATE QWT_MAKEDLL)
+endif()
 
 target_include_directories(omqwt
   PUBLIC