Fix invalid pointer conversions

C does not allow conversions between data pointers and function
pointers.

Yes, the name of the macro is reserved.  That's something for a future
commit to fix.

Fixes #1703

src/init.c

@@ -440,7 +440,7 @@ GLFWAPI int glfwGetError(const char** description)
 
 GLFWAPI GLFWerrorfun glfwSetErrorCallback(GLFWerrorfun cbfun)
 {
-    _GLFW_SWAP_POINTERS(_glfwErrorCallback, cbfun);
+    _GLFW_SWAP(GLFWerrorfun, _glfwErrorCallback, cbfun);
     return cbfun;
 }
 

src/input.c

@@ -868,7 +868,7 @@ GLFWAPI GLFWkeyfun glfwSetKeyCallback(GLFWwindow* handle, GLFWkeyfun cbfun)
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.key, cbfun);
+    _GLFW_SWAP(GLFWkeyfun, window->callbacks.key, cbfun);
     return cbfun;
 }
 
@@ -878,7 +878,7 @@ GLFWAPI GLFWcharfun glfwSetCharCallback(GLFWwindow* handle, GLFWcharfun cbfun)
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.character, cbfun);
+    _GLFW_SWAP(GLFWcharfun, window->callbacks.character, cbfun);
     return cbfun;
 }
 
@@ -888,7 +888,7 @@ GLFWAPI GLFWcharmodsfun glfwSetCharModsCallback(GLFWwindow* handle, GLFWcharmods
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.charmods, cbfun);
+    _GLFW_SWAP(GLFWcharmodsfun, window->callbacks.charmods, cbfun);
     return cbfun;
 }
 
@@ -899,7 +899,7 @@ GLFWAPI GLFWmousebuttonfun glfwSetMouseButtonCallback(GLFWwindow* handle,
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.mouseButton, cbfun);
+    _GLFW_SWAP(GLFWmousebuttonfun, window->callbacks.mouseButton, cbfun);
     return cbfun;
 }
 
@@ -910,7 +910,7 @@ GLFWAPI GLFWcursorposfun glfwSetCursorPosCallback(GLFWwindow* handle,
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.cursorPos, cbfun);
+    _GLFW_SWAP(GLFWcursorposfun, window->callbacks.cursorPos, cbfun);
     return cbfun;
 }
 
@@ -921,7 +921,7 @@ GLFWAPI GLFWcursorenterfun glfwSetCursorEnterCallback(GLFWwindow* handle,
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.cursorEnter, cbfun);
+    _GLFW_SWAP(GLFWcursorenterfun, window->callbacks.cursorEnter, cbfun);
     return cbfun;
 }
 
@@ -932,7 +932,7 @@ GLFWAPI GLFWscrollfun glfwSetScrollCallback(GLFWwindow* handle,
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.scroll, cbfun);
+    _GLFW_SWAP(GLFWscrollfun, window->callbacks.scroll, cbfun);
     return cbfun;
 }
 
@@ -942,7 +942,7 @@ GLFWAPI GLFWdropfun glfwSetDropCallback(GLFWwindow* handle, GLFWdropfun cbfun)
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.drop, cbfun);
+    _GLFW_SWAP(GLFWdropfun, window->callbacks.drop, cbfun);
     return cbfun;
 }
 
@@ -1166,7 +1166,7 @@ GLFWAPI GLFWjoystickfun glfwSetJoystickCallback(GLFWjoystickfun cbfun)
     if (!initJoysticks())
         return NULL;
 
-    _GLFW_SWAP_POINTERS(_glfw.callbacks.joystick, cbfun);
+    _GLFW_SWAP(GLFWjoystickfun, _glfw.callbacks.joystick, cbfun);
     return cbfun;
 }
 

src/internal.h

@@ -357,12 +357,12 @@ typedef void (APIENTRY * PFN_vkVoidFunction)(void);
     }
 
 // Swaps the provided pointers
-#define _GLFW_SWAP_POINTERS(x, y) \
-    {                             \
-        void* t;                  \
-        t = x;                    \
-        x = y;                    \
-        y = t;                    \
+#define _GLFW_SWAP(type, x, y) \
+    {                          \
+        type t;                \
+        t = x;                 \
+        x = y;                 \
+        y = t;                 \
     }
 
 // Per-thread error structure

src/monitor.c

@@ -419,7 +419,7 @@ GLFWAPI void* glfwGetMonitorUserPointer(GLFWmonitor* handle)
 GLFWAPI GLFWmonitorfun glfwSetMonitorCallback(GLFWmonitorfun cbfun)
 {
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(_glfw.callbacks.monitor, cbfun);
+    _GLFW_SWAP(GLFWmonitorfun, _glfw.callbacks.monitor, cbfun);
     return cbfun;
 }
 

src/window.c

@@ -992,7 +992,7 @@ GLFWAPI GLFWwindowposfun glfwSetWindowPosCallback(GLFWwindow* handle,
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.pos, cbfun);
+    _GLFW_SWAP(GLFWwindowposfun, window->callbacks.pos, cbfun);
     return cbfun;
 }
 
@@ -1003,7 +1003,7 @@ GLFWAPI GLFWwindowsizefun glfwSetWindowSizeCallback(GLFWwindow* handle,
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.size, cbfun);
+    _GLFW_SWAP(GLFWwindowsizefun, window->callbacks.size, cbfun);
     return cbfun;
 }
 
@@ -1014,7 +1014,7 @@ GLFWAPI GLFWwindowclosefun glfwSetWindowCloseCallback(GLFWwindow* handle,
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.close, cbfun);
+    _GLFW_SWAP(GLFWwindowclosefun, window->callbacks.close, cbfun);
     return cbfun;
 }
 
@@ -1025,7 +1025,7 @@ GLFWAPI GLFWwindowrefreshfun glfwSetWindowRefreshCallback(GLFWwindow* handle,
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.refresh, cbfun);
+    _GLFW_SWAP(GLFWwindowrefreshfun, window->callbacks.refresh, cbfun);
     return cbfun;
 }
 
@@ -1036,7 +1036,7 @@ GLFWAPI GLFWwindowfocusfun glfwSetWindowFocusCallback(GLFWwindow* handle,
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.focus, cbfun);
+    _GLFW_SWAP(GLFWwindowfocusfun, window->callbacks.focus, cbfun);
     return cbfun;
 }
 
@@ -1047,7 +1047,7 @@ GLFWAPI GLFWwindowiconifyfun glfwSetWindowIconifyCallback(GLFWwindow* handle,
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.iconify, cbfun);
+    _GLFW_SWAP(GLFWwindowiconifyfun, window->callbacks.iconify, cbfun);
     return cbfun;
 }
 
@@ -1058,7 +1058,7 @@ GLFWAPI GLFWwindowmaximizefun glfwSetWindowMaximizeCallback(GLFWwindow* handle,
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.maximize, cbfun);
+    _GLFW_SWAP(GLFWwindowmaximizefun, window->callbacks.maximize, cbfun);
     return cbfun;
 }
 
@@ -1069,7 +1069,7 @@ GLFWAPI GLFWframebuffersizefun glfwSetFramebufferSizeCallback(GLFWwindow* handle
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.fbsize, cbfun);
+    _GLFW_SWAP(GLFWframebuffersizefun, window->callbacks.fbsize, cbfun);
     return cbfun;
 }
 
@@ -1080,7 +1080,7 @@ GLFWAPI GLFWwindowcontentscalefun glfwSetWindowContentScaleCallback(GLFWwindow*
     assert(window != NULL);
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
-    _GLFW_SWAP_POINTERS(window->callbacks.scale, cbfun);
+    _GLFW_SWAP(GLFWwindowcontentscalefun, window->callbacks.scale, cbfun);
     return cbfun;
 }