Trouble building C library (with makefile)

Question

I'm doing a project in which I need to connect to an AR.Drone 2.0. I have a functional GUI in Java, but to control the drone I have to use it's SDK which is a C library. I wrote the necessary functions to combine Java and C via JNI, but because of the modifications I did to an example delivered with the SDK, it doesn't build anymore. It is thought to be built with a makefile (which I also have tried changing without success) running the make command. The problem is I am very new to C and makefiles, and I have searched the web a lot but have not found any solution. So here's how the library looks like:

.: Folder root
|
+ src: Sources
|
+ ARDroneLib: The AR.Drone Library
| |
| + Soft: Containing the "interesting" part of the whole lib
| | |
| | + More subdirs... (Build: contains a makefile, Common: c and h files, Lib: stuff)
| |
| + Many other subdirectories (FFMPEG, ITTIAM, VLIB, VP_SDK)
|
+ DroneControl: My own code
     |
     + Source:The source files
     | |
     | + Navdata: Code to retrieve the navigation data
     | | |
     | | + navdata.c
     | | + navdata.h
     | |
     | + Video: Code to retrieve the drone's video stream
     | | |
     | | + video_stage.c
     | | + video_stage.h
     | |
     | + ardrone_testing_tool.c: Main file, containing the main function, etc.
     | + ardrone_testing_tool.h: Its header
     | + dronecontrol_ARDrone: My own file, containing JNI methods (also has an init() function which calls main() in ardrone_testing_tool.c)
     | + dronecontrol_ARDrone: Its header
     | + vars.h:     Some shared variables
     |
     + Build:Contains the makefile
         |
         + makefile: The makefile

Here's the makefile in ./src/DroneControl/Build/:

SDK_PATH:=$(shell pwd)/../../ARDroneLib
PC_TARGET=yes
USE_LINUX=yes
ifdef MYKONOS
include $(ARDRONE_CUSTOM_CONFIG)
include $(ARDRONE_BUILD_CONFIG)
else
include $(SDK_PATH)/Soft/Build/custom.makefile
include $(SDK_PATH)/Soft/Build/config.makefile
endif
ifeq "$(RELEASE_BUILD)" "yes"
ARDRONE_TARGET_DIR=$(shell pwd)/../../../
else
ARDRONE_TARGET_DIR=$(shell pwd)/../../../Debug
endif
TARGET=linux_sdk_demo
SRC_DIR:=$(shell pwd)/../Sources
# Define application source files
GENERIC_BINARIES_SOURCE_DIR:=$(SRC_DIR)
GENERIC_BINARIES_COMMON_SOURCE_FILES+= \
Navdata/navdata.c \
Video/video_stage.c
GENERIC_INCLUDES+=     \
$(SRC_DIR) \
$(LIB_DIR) \
$(SDK_PATH)/Soft/Common \
$(SDK_PATH)/Soft/Lib
GENERIC_TARGET_BINARIES_PREFIX=
GENERIC_TARGET_BINARIES_DIR=$(ARDRONE_TARGET_DIR)
GENERIC_BINARIES_SOURCE_ENTRYPOINTS+= \
ardrone_testing_tool.c
GENERIC_INCLUDES:=$(addprefix -I,$(GENERIC_INCLUDES))
GENERIC_LIB_PATHS=-L$(GENERIC_TARGET_BINARIES_DIR)
GENERIC_LIBS=-lpc_ardrone -lgtk-x11-2.0 -lrt
SDK_FLAGS+="USE_APP=yes"
SDK_FLAGS+="APP_ID=linux_sdk_demo"
export GENERIC_CFLAGS
export GENERIC_LIBS
export GENERIC_LIB_PATHS
export GENERIC_INCLUDES
export GENERIC_BINARIES_SOURCE_DIR
export GENERIC_BINARIES_COMMON_SOURCE_FILES
export GENERIC_TARGET_BINARIES_PREFIX
export GENERIC_TARGET_BINARIES_DIR
export GENERIC_BINARIES_SOURCE_ENTRYPOINTS
export GENERIC_LIBRARY_SOURCE_DIR=$(GENERIC_BINARIES_SOURCE_DIR)

.PHONY: $(TARGET) build_libs
all: build_libs $(TARGET)
$(TARGET):
@$(MAKE) -C $(SDK_PATH)/VP_SDK/Build $(TMP_SDK_FLAGS) $(SDK_FLAGS) $(MAKECMDGOALS) USE_LINUX=yes
mv $(ARDRONE_TARGET_DIR)/ardrone_testing_tool $(TARGET)
mv $(TARGET) $(ARDRONE_TARGET_DIR)/
$(MAKECMDGOALS): build_libs
@$(MAKE) -C $(SDK_PATH)/VP_SDK/Build $(TMP_SDK_FLAGS) $(SDK_FLAGS) $(MAKECMDGOALS) USE_LINUX=yes
build_libs:
@$(MAKE) -C $(SDK_PATH)/Soft/Build $(TMP_SDK_FLAGS) $(SDK_FLAGS) $(MAKECMDGOALS) USE_LINUX=yes

But when I try to make this, the make command gives me following error:

Libs already extracted
Building target static
/bin/sh: 1: ./autoConf.bash: Permission denied
make[2]: *** [build] Error 126
Checking required Ubuntu packages ...
ok.
Building ARDroneTool/Lib
Building ARDroneTool/Lib
ld ardrone_testing_tool
/usr/bin/ld: cannot find -lswscale
/usr/bin/ld: cannot find -lavformat
/usr/bin/ld: cannot find -lavcodec
/usr/bin/ld: cannot find -lavutil
collect2: ld returned 1 exit status
make[3]: *** [/home/user/workspace/AutoFlight/lib/native/DroneControl/src/DroneControl/Build/../../..//ardrone_testing_tool] Error 1
make[2]: *** [all] Error 2
make[1]: *** [build_app] Error 2
make: *** [linux_sdk_demo] Error 2

I have not been able to figure out what -lwscale, -lavformat, etc. are. I have also tried the make command as su (mainly because that "Permission denied" error), and hope this is the right place to ask this. So does anybody have suggestions on how to get this compiled into a dynamically linked library (.so file)? Any help would be highly appreciated!

UPDATE 1: The permission denied error is now solved (thanks @eyalm)

UPDATE 2: It works now. I've rewritten the makefile but I don't know what's different now that could affect ld 's path.

Answer 1

autoConf.bash is probably not executable. Running with su will not help. try:

# chmod a+x autoConf.bash

Answer 2

> /usr/bin/ld: cannot find -lswscale
> /usr/bin/ld: cannot find -lavformat
> /usr/bin/ld: cannot find -lavcodec
> /usr/bin/ld: cannot find -lavutil
> collect2: ld returned 1 exit status

It could be that these dependencies (ie, libswscale , libavformat , libavcodec , and libavutil ) are either not present on your system, or are present in directories that are not part of ld 's standard search path.

If the dependencies are absent, then you would need to install them. On Debian-derived systems you could use the apt-file command to find the package you would need to install. For example:

% apt-file -l find libswscale.a
libswscale-dev
% apt-file -l find libavutil.a
libavutil-dev
...etc...

If these libraries are already present on your system, but are in non-standard locations, you could use ld 's -L option to add the relevant directories to its search path. For example:

% ld ..other-options... -L SEARCHDIR1 -L SEARCHDIR2 ... -lswscale -lavutil ...etc...

Note that the -L SEARCHDIR options need to appear before the -l LIB options.