How to compile a dll which needs other dlls - c

Question

I'm trying to cross compile a piece of software I'm doing.
I'm on Linux and I'm having a pretty hard time trying to write a Makefile for compiling a DLL library using SDL2. Here is it:
#the compiler
CC = i686-w64-mingw32-gcc
#the standart ompilation flags of the project
CFLAGS = -O3 -Wall -Wno-unused-variable -Wno-unused-but-set-variable -Wno-implicit-function-declaration
#path to the folder's root, where the holy not build framework is. Relate to this Makefile
PREPATH = ..
#Path to the SDL, SDL_image and Lua includes and libs
SDL2INCLUDES = -I $(PREPATH)/SDL2/include
SDL2LIBS = $(PREPATH)/BINARIES/4windows/SDL2/64/SDL2.dll
SDLIMAGE2INCLUDES = -I $(PREPATH)/SDL2/SDL_image
SDLIMAGE2LIBS = $(PREPATH)/BINARIES/4windows/SDL2_image/64/SDL2_image.dll $(PREPATH)/BINARIES/4windows/SDL2_image/64/libjpeg-9.dll $(PREPATH)/BINARIES/4windows/SDL2_image/64/libpng16-16.dll $(PREPATH)/BINARIES/4windows/SDL2_image/64/libtiff-5.dll $(PREPATH)/BINARIES/4windows/SDL2_image/64/libwebp-4.dll $(PREPATH)/BINARIES/4windows/SDL2_image/64/zlib1.dll
#LUAINCLUDES = -I $(PREPATH)/lua/
#LUALIB = $(PREPATH)/lua/ -llua -lm
#Where to put the compiled program
COMPILEPATH = $(PREPATH)/BINARIES/
#Build options
build: NLF.o
cp ./*.o $(COMPILEPATH)
$(CC) $(CFLAGS) -shared -o $(COMPILEPATH)libNLF.dll $(SDL2LIBS) $(SDLIMAGE2LIBS) $(COMPILEPATH)*.o
NLF.o: NLF_osservice.o NLF_error.o NLF_screen.o NLF.h.gch
$(CC) -c -DBUILD_DLL $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) NLF.c
NLF.h.gch: NLF.h
$(CC) $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) NLF.h
NLF_osservice.o: NLF_osservice.h.gch
$(CC) -c -DBUILD_DLL $(CFLAGS) $(SDL2INCLUDES) NLF_osservice.c
NLF_osservice.h.gch:
$(CC) $(CFLAGS) $(SDL2INCLUDES) NLF_osservice.h
NLF_error.o: NLF_error.h.gch
$(CC) -c -DBUILD_DLL $(CFLAGS) $(SDL2INCLUDES) NLF_error.c
NLF_error.h.gch:
$(CC) $(CFLAGS) $(SDL2INCLUDES) NLF_error.h
NLF_screen.o: NLF_screen.h.gch
$(CC) -c -DBUILD_DLL $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) NLF_screen.c
NLF_screen.h.gch:
$(CC) $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) NLF_screen.h
#cleaning options
clean-build:
rm -f -v $(COMPILEPATH)*.o
clean-all:
rm -f -v ./*.o ./*.h.gch
rm -f -v $(COMPILEPATH)*.o $(COMPILEPATH)*.so
clean-soft:
rm -f -v ./*.o ./*.h.gch
rm -f -v $(COMPILEPATH)*.o
When running make all, the compilation runs fine, but when it gets to the -shared part, I get this:
../BINARIES/4windows/SDL2/64/SDL2.dll: file not recognized:
I tried to add -L before the Third Party DLL, like this:
SDL2LIBS = -L $(PREPATH)/BINARIES/4windows/SDL2/64/SDL2.dll
SDLIMAGE2LIBS = -L $(PREPATH)/BINARIES/4windows/SDL2_image/64/SDL2_image.dll -L $(PREPATH)/BINARIES/4windows/SDL2_image/64/libjpeg-9.dll -L $(PREPATH)/BINARIES/4windows/SDL2_image/64/libpng16-16.dll -L $(PREPATH)/BINARIES/4windows/SDL2_image/64/libtiff-5.dll -L $(PREPATH)/BINARIES/4windows/SDL2_image/64/libwebp-4.dll -L $(PREPATH)/BINARIES/4windows/SDL2_image/64/zlib1.dll
And then I get undefined reference errors...
The same error if I change the line:
$(CC) $(CFLAGS) -shared -o $(COMPILEPATH)libNLF.dll $(SDL2LIBS) $(SDLIMAGE2LIBS) $(COMPILEPATH)*.o
for
$(CC) $(CFLAGS) $(SDL2LIBS) $(SDLIMAGE2LIBS) -shared -o $(COMPILEPATH)libNLF.dll $(COMPILEPATH)*.o
Does anyone know what's going on?

Answer 1

You should not use -L before library files. -L indicates a library path. For library files, you should use -l (lowercase L).
But, if you're indicating the path to the file, and are including the file extension, you don't need to use -l, though. So the initial Makefile was correct in that sense.
You should provide the full error that you got, not just file not recognized:. I bet this is a file format not recognized error, which probably indicates that you should not be linking against a .dll file, but .lib files. Similar problem here.

Answer 2

I've solved!! here is how
Putting these files within the SDL path:
libSDL2.a, libSDL2.dll.a, libSDL2main.a, libSDL2_test.a, SDL2.lib, SDL2main.lib, and SDL2test.lib
And these with the SDL_image one.:
libSDL2_image.a and libSDL2_image.dll.a
And here is the Makefile:
#the compiler
CC = i686-w64-mingw32-gcc
#the standart ompilation flags of the project
CFLAGS = -O3 -Wall -Wno-unused-variable -Wno-unused-but-set-variable -Wno-implicit-function-declaration
#path to the folder's root, where the holy not build framework is. Relate to this Makefile
PREPATH = ..
#Path to the SDL, SDL_image and Lua includes and libs
SDL2INCLUDES = -I $DS(PREPATH)/SDL2/include
SDL2LIBS = -L$(PREPATH)/SDL2/4windows/SDL2/64 -lmingw32 -lSDL2main -lSDL2
SDLIMAGE2INCLUDES = -I $(PREPATH)/SDL2/SDL_image
SDLIMAGE2LIBS = -L$(PREPATH)/SDL2/4windows/SDL2_image/64 -lSDL2_image
#LUAINCLUDES = -I $(PREPATH)/lua/
#LUALIB = -L $(PREPATH)/lua/ -llua -lm
#Where to put the compiled program
COMPILEPATH = $(PREPATH)/BINARIES/
#Build options
build: NLF.o
cp ./*.o $(COMPILEPATH)
$(CC) $(CFLAGS) -shared $(COMPILEPATH)*.o $(SDL2LIBS) $(SDLIMAGE2LIBS) -o $(COMPILEPATH)libNLF.dll
NLF.o: NLF_osservice.o NLF_error.o NLF_screen.o NLF.h.gch
$(CC) -c -DBUILD_DLL $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) NLF.c
NLF.h.gch: NLF.h
$(CC) $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) NLF.h
NLF_osservice.o: NLF_osservice.h.gch
$(CC) -c -DBUILD_DLL $(CFLAGS) $(SDL2INCLUDES) NLF_osservice.c
NLF_osservice.h.gch:
$(CC) $(CFLAGS) $(SDL2INCLUDES) NLF_osservice.h
NLF_error.o: NLF_error.h.gch
$(CC) -c -DBUILD_DLL $(CFLAGS) $(SDL2INCLUDES) NLF_error.c
NLF_error.h.gch:
$(CC) $(CFLAGS) $(SDL2INCLUDES) NLF_error.h
NLF_screen.o: NLF_screen.h.gch
$(CC) -c -DBUILD_DLL $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) NLF_screen.c
NLF_screen.h.gch:
$(CC) $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) NLF_screen.h
#cleaning options
clean-build:
rm -f -v $(COMPILEPATH)*.o
clean-all:
rm -f -v ./*.o ./*.h.gch
rm -f -v $(COMPILEPATH)*.o $(COMPILEPATH)*.dll
clean-soft:
rm -f -v ./*.o ./*.h.gch
rm -f -v $(COMPILEPATH)*.o
Now my new problem is how to compile all this stuff to 32 bits windows. But it is an statement for another question.