Linking a jpeglib to in makefile

Question

Hi I am trying to use jpeglib in my code and i have trouble linking it with my Makefile I downloaded it in tar.gz file then extracted it and did all the ./configure then the makes and all this stuff but now I have to link it in Makefile and I dunno how here is the Makefile

CFLAGS+= -Wall -Werror -fPIE -std=gnu99 -g
LDFLAGS=  -pthread 

HW=prgsem
BINARIES=prgsem

#LDFLAGS += -L/usr/local/lib -ljpeglib
#CXXFLAGS += -I/usr/local/include
CFLAGS+=$(shell sdl2-config --cflags)
LDFLAGS+=$(shell sdl2-config --libs) -lSDL2_image



all: ${BINARIES}

OBJS=${patsubst %.c,%.o,${wildcard *.c}}

prgsem: ${OBJS}
    ${CC} ${OBJS} ${CXXFLAGS}  ${LDFLAGS} -o $@

${OBJS}: %.o: %.c
    ${CC} -c ${CFLAGS}  $< -o $@

clean:
    rm -f ${BINARIES} ${OBJS}

The commented stuff is what I tried and didnt work. Also I tried to change the #include itself. Tried #include "jpeglib.h" also #include <jpeglib.h> nothing worked.

EDIT: added make compile error message

cc xwin_sdl.o event_queue.o prg_io_nonblock.o gui.o main.o prgsem.o messages.o keyboard.o computation.o utils.o   -pthread  -L/usr/local/lib -Wl,-rpath,/usr/local/lib -Wl,--enable-new-dtags -lSDL2 -lSDL2_image -o prgsem
/usr/bin/ld: gui.o: in function `save_img':
/home/peter/Cprog/bab36prga-sem/gui.c:67: undefined reference to `jpeg_std_error'
/usr/bin/ld: /home/peter/Cprog/bab36prga-sem/gui.c:69: undefined reference to `jpeg_CreateCompress'
/usr/bin/ld: /home/peter/Cprog/bab36prga-sem/gui.c:74: undefined reference to `jpeg_stdio_dest'
/usr/bin/ld: /home/peter/Cprog/bab36prga-sem/gui.c:81: undefined reference to `jpeg_set_defaults'
/usr/bin/ld: /home/peter/Cprog/bab36prga-sem/gui.c:83: undefined reference to `jpeg_start_compress'
/usr/bin/ld: /home/peter/Cprog/bab36prga-sem/gui.c:90: undefined reference to `jpeg_write_scanlines'
/usr/bin/ld: /home/peter/Cprog/bab36prga-sem/gui.c:93: undefined reference to `jpeg_finish_compress'
/usr/bin/ld: /home/peter/Cprog/bab36prga-sem/gui.c:97: undefined reference to `jpeg_destroy_compress'
collect2: error: ld returned 1 exit status
make: *** [Makefile:19: prgsem] Error 1

Thanks for any answers.

Answer 1

Your problem is not during the compilation phase of your program, so changing the #include etc. won't help in this case.

Your problem is during the linking phase, so that means you have not added the library to your link line. If, for example, the library is named libjpeg.a or libjpeg.so , then you need to add -ljpeg to your link line. The easiest way is to add it to the end of LDFLAGS :

LDFLAGS+=$(shell sdl2-config --libs) -lSDL2_image -ljpeg