wmain: build as c++ instead of c

Allows to keep exiv2 c++ only.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

app/CMakeLists.txt

@@ -28,7 +28,7 @@ target_link_libraries(exiv2 PRIVATE std::filesystem)
 if(MSVC OR MINGW)
     # Trick to get properly UTF-8 encoded argv 
     # More info at: https://github.com/huangqinjin/wmain
-    add_library(wmain STATIC wmain.c)
+    add_library(wmain STATIC wmain.cpp)
     target_link_libraries(exiv2 PRIVATE wmain)
 endif()
 

app/wmain.cpp

@@ -2,23 +2,23 @@
 
 #include <windows.h>
 
-extern int __cdecl main();
+extern int __cdecl main(int, char*[]);
 
 int wmain(int argc, wchar_t* argv[]) {
   char** args;
-  int nbytes = (int)(sizeof(char*) * (argc + 1));
+  int nbytes = static_cast<int>(sizeof(char*) * (argc + 1));
   HANDLE heap = GetProcessHeap();
 
   for (int i = 0; i < argc; ++i)
-    nbytes += WideCharToMultiByte(CP_UTF8, 0, argv[i], -1, NULL, 0, NULL, NULL);
+    nbytes += WideCharToMultiByte(CP_UTF8, 0, argv[i], -1, nullptr, 0, nullptr, nullptr);
 
-  args = HeapAlloc(heap, 0, nbytes);
+  args = reinterpret_cast<char**>(HeapAlloc(heap, 0, nbytes));
-  args[0] = (char*)(args + argc + 1);
+  args[0] = reinterpret_cast<char*>(args + argc + 1);
 
   for (int i = 0; i < argc; ++i)
-    args[i + 1] = args[i] + WideCharToMultiByte(CP_UTF8, 0, argv[i], -1, args[i], nbytes, NULL, NULL);
+    args[i + 1] = args[i] + WideCharToMultiByte(CP_UTF8, 0, argv[i], -1, args[i], nbytes, nullptr, nullptr);
 
-  args[argc] = NULL;
+  args[argc] = nullptr;
 
   argc = main(argc, args);
   HeapFree(heap, 0, args);