makefile gcc自定义动态lib链接问题与.so文件

Question

Guys I'm having a very hard time trying to make a custom .so file be correctly linked with the a another code file.

Where is the Makefile of the who creates the .so file:

#the compiler
CC = 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)SDL2/lib/libSDL2-2.0.so.0 $(PREPATH)SDL2/lib/libSDL2_test.a $(PREPATH)SDL2/lib/libSDL2-2.0.so.0.2.1 $(PREPATH)SDL2/lib/libSDL2main.a $(PREPATH)SDL2/lib/libSDL2.a $(PREPATH)SDL2/lib/libSDL2.so
SDLIMAGE2INCLUDES = -I $(PREPATH)SDL2/SDL_image
SDLIMAGE2LIBS = $(PREPATH)SDL2/lib/libSDL2_image-2.0.so.0 $(PREPATH)SDL2/lib/libSDL2_image.so $(PREPATH)SDL2/lib/libSDL2_image-2.0.so.0.0.0 $(PREPATH)SDL2/lib/libSDL2_image.a
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) -shared $(CFLAGS) $(SDL2INCLUDES) $(SDL2LIBS) $(SDLIMAGE2INCLUDES) $(SDLIMAGE2LIBS) $(LUAINCLUDES) $(LUALIB) $(COMPILEPATH)*.o -o $(COMPILEPATH)libNLF.so

NLF.o: NLF_osservice.o NLF_Error.o NLF_event.o NLF.h.gch
    $(CC) $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) $(LUAINCLUDES) -fPIC -c NLF.c

NLF.h.gch: NLF.h
    $(CC) $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) $(LUAINCLUDES) NLF.h

NLF_osservice.o: NLF_osservice.h.gch
    $(CC) $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) $(LUAINCLUDES) $(NLFINCLUDES) -fPIC -c NLF_osservice.c
NLF_osservice.h.gch:
    $(CC) $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) $(LUAINCLUDES) $(NLFINCLUDES) NLF_osservice.h

NLF_Error.o: NLF_error.h.gch
    $(CC) $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) $(LUAINCLUDES) $(NLFINCLUDES) -fPIC -c NLF_error.c
NLF_error.h.gch:
    $(CC) $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) $(LUAINCLUDES) $(NLFINCLUDES) NLF_error.h

NLF_event.o: NLF_event.h.gch
    $(CC) $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) $(LUAINCLUDES) $(NLFINCLUDES) -fPIC -c NLF_event.c
NLF_event.h.gch:
    $(CC) $(CFLAGS) $(SDL2INCLUDES) $(SDLIMAGE2INCLUDES) $(LUAINCLUDES) $(NLFINCLUDES) NLF_event.h  



#cleaning options

clean-build:
    rm -f -v $(COMPILEPATH)*.o

clean-hard clean-all:
    rm -f -v ./*.o ./*.h.gch
    rm -f -v $(COMPILEPATH)*.o $(COMPILEPATH)*.so

clean-soft clean-all-but-so:
    rm -f -v ./*.o ./*.h.gch

it's a bit long, but it's not hard ^^" This one compiles normally and create the "libNLF.so" file in the "BINARIES" folder. To be sure a run the command "nm -g libNLF.so | grep NLF", and it gives me between other things, this line:

0000000000001100 T NLF_init

Now lets to the problematic Makefile:

CC = gcc
CFLAGS = -O3
PREPATH = ../

SDL2INCLUDES = -I $(PREPATH)SDL2/include
SDL2LIBS = -L $(PREPATH)SDL2/lib/libSDL2-2.0.so.0 -L $(PREPATH)SDL2/lib/libSDL2_test.a -L $(PREPATH)SDL2/lib/libSDL2-2.0.so.0.2.1 -L $(PREPATH)SDL2/lib/libSDL2main.a -L $(PREPATH)SDL2/lib/libSDL2.a -L $(PREPATH)SDL2/lib/libSDL2.so
SDLIMAGE2INCLUDES = -I $(PREPATH)SDL2/SDL_image
SDLIMAGE2LIBS = -L $(PREPATH)SDL2/lib/libSDL2_image-2.0.so.0 -L $(PREPATH)SDL2/lib/libSDL2_image.so -L $(PREPATH)SDL2/lib/libSDL2_image-2.0.so.0.0.0 -L $(PREPATH)SDL2/lib/libSDL2_image.a
#LUAINCLUDES = -I $(PREPATH)lua/
#LUALIB = -L $(PREPATH)lua/ -llua -lm

NLFINCLUDES = -I $(PREPATH)NLF_SCR/
NLFLIB = -L ../BINARIES/libNLF.so


build:
    $(CC) $(CFLAGS) auto_genareted_code.c $(NLFINCLUDES) $(SDL2INCLUDES) $(NLFLIB) $(SDL2LIBS) -o auto_genareted_code

and the GCC gives me:

auto_genareted_code.c:(.text.startup+0x7): undefined reference to `NLF_init' and all other funtions from libNLF.so are in the same situation.

does some one knows what the hack in going on?

Answer 1

Adding to John Bollinger's solution, remember to put libraries linking at the end of compiler command, as order is important for library linking.

http://gcc.gnu.org/onlinedocs/gcc/Link-Options.html

It makes a difference where in the command you write this option; the linker searches and processes libraries and object files in the order they are specified. Thus, foo.o -lz bar.o' searches library z' after file foo.o but before bar.o. If bar.o refers to functions in `z', those functions may not be loaded.