SetWindowLongPtrで,コンパイルエラーになる

このサイトを参考に,ウィンドウプロシージャのすり替えをしようとしましたが,掲載されているソースコード(のGWL_WNDPROCをGWLP_WNDPROCに変えた)をコンパイルしようとすると,

test.cpp:34:48: error: cast from 'LRESULT (*)(HWND, UINT, WPARAM, LPARAM)' {aka 'long long int (*)(HWND__*, unsigned int, long long unsigned int, long long int)'} to 'LONG' {aka 'long int'}
loses precision [-fpermissive]
   SetWindowLong(rect_box , GWL_WNDPROC , (LONG)StaticProc);
                                                ^~~~~~~~~~

というエラーがでてしまいます。「数値からポインタにはキャストできないよー」という趣旨のエラーであることはわかるんですが,どう試してもエラーになるので途方に暮れています。

ソースコード

C++
1#include <windows.h>
2
3WNDPROC DefStaticProc;
4
5LRESULT CALLBACK StaticProc(HWND hwnd , UINT msg , WPARAM wp , LPARAM lp) {
6	switch(msg) {
7	case WM_NCHITTEST:
8		if (GetKeyState(VK_LBUTTON) < 0)
9			MessageBox(
10				hwnd , TEXT("Kitty on your lap") ,
11				TEXT("Kitty") , MB_OK
12			);
13		return 0;
14	}
15	return CallWindowProc(DefStaticProc , hwnd , msg , wp , lp);
16}
17
18LRESULT CALLBACK WndProc(HWND hwnd , UINT msg , WPARAM wp , LPARAM lp) {
19	static HWND rect_box;
20
21	switch (msg) {
22	case WM_DESTROY:
23		PostQuitMessage(0);
24		return 0;
25	case WM_CREATE:
26		rect_box = CreateWindow(
27			TEXT("STATIC") , TEXT("Kitty") ,
28			WS_CHILD | WS_VISIBLE ,
29			0 , 0 , 200 , 45 ,
30			hwnd , (HMENU)1 ,
31			((LPCREATESTRUCT)(lp))->hInstance , NULL
32		);
33		DefStaticProc = (WNDPROC)GetWindowLongPtr(rect_box , GWLP_WNDPROC);
34		SetWindowLongPtr(rect_box , GWLP_WNDPROC , (LONG)StaticProc);
35		return 0;
36	}
37	return DefWindowProc(hwnd , msg , wp , lp);
38}
39
40int WINAPI WinMain(HINSTANCE hInstance , HINSTANCE hPrevInstance ,
41			PSTR lpCmdLine , int nCmdShow ) {
42	HWND hwnd;
43	MSG msg;
44	WNDCLASS winc;
45
46	winc.style			= CS_HREDRAW | CS_VREDRAW;
47	winc.lpfnWndProc	= WndProc;
48	winc.cbClsExtra		= winc.cbWndExtra	= 0;
49	winc.hInstance		= hInstance;
50	winc.hIcon			= LoadIcon(NULL , IDI_APPLICATION);
51	winc.hCursor		= LoadCursor(NULL , IDC_ARROW);
52	winc.hbrBackground	= (HBRUSH)GetStockObject(WHITE_BRUSH);
53	winc.lpszMenuName	= NULL;
54	winc.lpszClassName	= TEXT("KITTY");
55
56	if (!RegisterClass(&winc)) return -1;
57
58	hwnd = CreateWindow(
59			TEXT("KITTY") , TEXT("Kitty on your lap") ,
60			WS_OVERLAPPEDWINDOW | WS_VISIBLE ,
61			CW_USEDEFAULT , CW_USEDEFAULT ,
62			CW_USEDEFAULT , CW_USEDEFAULT ,
63			NULL , NULL , hInstance , NULL
64	);
65
66	if (hwnd == NULL) return -1;
67
68	while(GetMessage(&msg , NULL , 0 , 0)) DispatchMessage(&msg);
69	return msg.wParam;
70}
71

環境

Windows8
MinGW-W64

gcc
1Using built-in specs.
2COLLECT_GCC=gcc
3COLLECT_LTO_WRAPPER=D:/Apps/MinGW-W64/mingw64/bin/../libexec/gcc/x86_64-w64-mingw32/8.1.0/lto-wrapper.exe
4Target: x86_64-w64-mingw32
5Configured with: ../../../src/gcc-8.1.0/configure --host=x86_64-w64-mingw32 --build=x86_64-w64-mingw32 --target=x86_64-w64-mingw32 --prefix=/mingw64 --with-sysroot=/c/mingw810/x86_64-810-pos
6ix-seh-rt_v6-rev0/mingw64 --enable-shared --enable-static --disable-multilib --enable-languages=c,c++,fortran,lto --enable-libstdcxx-time=yes --enable-threads=posix --enable-libgomp --enable
7-libatomic --enable-lto --enable-graphite --enable-checking=release --enable-fully-dynamic-string --enable-version-specific-runtime-libs --disable-libstdcxx-pch --disable-libstdcxx-debug --e
8nable-bootstrap --disable-rpath --disable-win32-registry --disable-nls --disable-werror --disable-symvers --with-gnu-as --with-gnu-ld --with-arch=nocona --with-tune=core2 --with-libiconv --w
9ith-system-zlib --with-gmp=/c/mingw810/prerequisites/x86_64-w64-mingw32-static --with-mpfr=/c/mingw810/prerequisites/x86_64-w64-mingw32-static --with-mpc=/c/mingw810/prerequisites/x86_64-w64
10-mingw32-static --with-isl=/c/mingw810/prerequisites/x86_64-w64-mingw32-static --with-pkgversion='x86_64-posix-seh-rev0, Built by MinGW-W64 project' --with-bugurl=https://sourceforge.net/pro
11jects/mingw-w64 CFLAGS='-O2 -pipe -fno-ident -I/c/mingw810/x86_64-810-posix-seh-rt_v6-rev0/mingw64/opt/include -I/c/mingw810/prerequisites/x86_64-zlib-static/include -I/c/mingw810/prerequisi
12tes/x86_64-w64-mingw32-static/include' CXXFLAGS='-O2 -pipe -fno-ident -I/c/mingw810/x86_64-810-posix-seh-rt_v6-rev0/mingw64/opt/include -I/c/mingw810/prerequisites/x86_64-zlib-static/include
13 -I/c/mingw810/prerequisites/x86_64-w64-mingw32-static/include' CPPFLAGS=' -I/c/mingw810/x86_64-810-posix-seh-rt_v6-rev0/mingw64/opt/include -I/c/mingw810/prerequisites/x86_64-zlib-static/in
14clude -I/c/mingw810/prerequisites/x86_64-w64-mingw32-static/include' LDFLAGS='-pipe -fno-ident -L/c/mingw810/x86_64-810-posix-seh-rt_v6-rev0/mingw64/opt/lib -L/c/mingw810/prerequisites/x86_6
154-zlib-static/lib -L/c/mingw810/prerequisites/x86_64-w64-mingw32-static/lib '
16Thread model: posix
17gcc version 8.1.0 (x86_64-posix-seh-rev0, Built by MinGW-W64 project)