OpenEuphoria

2. Re: Can't get DLL to Build

• Posted by ghaberek (admin) in July
• 299 views

CFLAGS += -I../.. -Os -s -DTIGR_SHARED 
ifeq ($(OS),Windows_NT) 
	LDFLAGS += -s -lopengl32 -lgdi32 
	DLL = dll 
	EXT = exe 
else 
	UNAME_S := $(shell uname -s) 
	DLL = so 
	EXT =  
	ifeq ($(UNAME_S),Darwin) 
		LDFLAGS += -framework OpenGL -framework Cocoa 
	else ifeq ($(UNAME_S),Linux) 
		LDFLAGS += -s -lGLU -lGL -lX11 
	endif 
endif 
 
 
hello.$(EXT) : hello.c tigr.$(DLL)  
	gcc $^ -Os -o $@ $(CFLAGS) $(LDFLAGS) 
 
tigr.$(DLL): 
	gcc ../../tigr.c -DTIGR_BUILDSHARED -shared $(CFLAGS) $(LDFLAGS) -o tigr.$(DLL) 
 
clean: 
	rm hello.$(ext) 

That's a weird looking Makefile. I guess it's not wrong per se, but on a non-Windows platform you'd end up with an executable named "hello." with a trailing dot. Strange.

undefined reference to `__mingw_winmain_hInstance' 
undefined reference to `__mingw_winmain_lpCmdLine' 
undefined reference to `__mingw_winmain_nShowCmd' 

That's because the original tigr.c defines its own WinMain() function here, which assumes you're building an executable and not a shared library. You can't have a main() (or WinMain()) function in a shared library.

gcc -c tigr.c 

That's because you're only compiling the source file, so the linker isn't yet looking for WinMain(). In order to build this correctly you'll need to add an #ifdef guard to tigr.c that blocks out WinMain().

2699	#ifndef TIGR_BUILDSHARED // ADD THIS LINE 
2700	// We supply our own WinMain and just chain through to the user's 
2701	// real entry point. 
2702	#ifdef UNICODE 
2703	int CALLBACK wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmdLine, int nCmdShow) 
2704	#else 
2705	int CALLBACK WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) 
2706	#endif 
2707	{ 
2708	    int n, argc; 
2709	    LPWSTR* wargv = CommandLineToArgvW(GetCommandLineW(), &argc); 
2710	    char** argv = (char**)calloc(argc + 1, sizeof(int)); 
2711	 
2712	    (void)hInstance; 
2713	    (void)hPrevInstance; 
2714	    (void)lpCmdLine; 
2715	    (void)nCmdShow; 
2716	 
2717	    for (n = 0; n < argc; n++) { 
2718	        int len = WideCharToMultiByte(CP_UTF8, 0, wargv[n], -1, 0, 0, NULL, NULL); 
2719	        argv[n] = (char*)malloc(len); 
2720	        WideCharToMultiByte(CP_UTF8, 0, wargv[n], -1, argv[n], len, NULL, NULL); 
2721	    } 
2722	    return main(argc, argv); 
2723	} 
2724	#endif // ADD THIS LINE 
2725	#endif 

(Note that there will now be two #endif lines after the WinMain() function. The original #endif is from #ifdef _WIN32 up at line 1947.)

Here is a Makefile you can use to build a shared library. Place this in the root of the project directory next to tigr.c and tigr.h.

CFLAGS += -Os -s 
LDFLAGS += -shared 
ifeq ($(OS),Windows_NT) 
	CFLAGS += -DTIGR_SHARED 
	LDLIBS += -lopengl32 -lgdi32 
	LIBEXT := .dll 
else 
	CFLAGS += -fPIC 
	LIBPRE := lib 
	UNAME_S := $(shell uname -s) 
	ifeq ($(UNAME_S),Darwin) 
		LDLIBS += -framework OpenGL -framework Cocoa 
		LIBEXT := .dylib 
	else 
		LDLIBS += -lGLU -lGL -lX11 
		LIBEXT := .so 
	endif 
endif 
 
$(LIBPRE)tigr$(LIBEXT): tigr.c 
	gcc $(CFLAGS) -DTIGR_BUILDSHARED $(LDFLAGS) -o $@ $< $(LDLIBS) 

If you're just building on Windows you can use this simplified version:

tigr.dll: tigr.c 
	gcc -Os -s -DTIGR_SHARED -DTIGR_BUILDSHARED -shared -o $@ $< -lopengl32 -lgdi32 

-Greg