I am attempting to compile third party code to a shared library so I can call it from Python using ctypes. This is my first time knowingly working with shared libraries.
I build the object code using:
gcc -c -fPIC -o elisa3-lib.o ../elisa3-lib.c
gcc -c -fPIC -o usb-comm.o ../usb-comm.c
Then I attempt to build the shared library:
gcc -shared -fPIC -Wl,-install_name,libelisa3.so -o libelisa3.so.1.0 elisa3-lib.o usb-comm.o -lc
And I get linker errors because usbcomm.c references libusb.h:
#ifdef __APPLE__
#include </opt/local/include/libusb-1.0/libusb.h>
#endif
With errors:
Undefined symbols for architecture x86_64:
"_libusb_bulk_transfer", referenced from:
_usb_send in usb-comm.o
_usb_receive in usb-comm.o
"_libusb_claim_interface", referenced from:
_openCommunication in usb-comm.o
"_libusb_close", referenced from:
_closeCommunication in usb-comm.o
"_libusb_exit", referenced from:
_closeCommunication in usb-comm.o
"_libusb_init", referenced from:
_openCommunication in usb-comm.o
"_libusb_open_device_with_vid_pid", referenced from:
_find_nrf_device in usb-comm.o
"_libusb_release_interface", referenced from:
_closeCommunication in usb-comm.o
ld: symbol(s) not found for architecture x86_64
How do I link correctly? Do I need to compile libusb to a shared library as well and link with -l?
"Undefined symbols" are functions/variables that the linker can't find. In short, yes you need to include libusb as either one of the libraries or objects you're linking in. Do whichever is easier or more appropriate.
Related
I am trying to test Jansson on Xcode 7.3.1. I installed according to the instructions, then used cMake when that didn't work, which also didn't work. I think Xcode is having trouble finding the Jansson library. I have modified the project header and library paths in many different ways, after extensive suggestions from searching out this problem. Xcode is able to find the header. Note also that I am able to install Jansson and run it in Eclipse. Any insight would be appreciated.
Here is the error log from Xcode:
Ld /Users/corrychapman/Library/Developer/Xcode/DerivedData/JanssonDev-dispcmnteuwiedaiazlbkwtztfcu/Build/Products/Debug/JanssonDev normal x86_64
cd /Users/corrychapman/Desktop/jansson-2.11/JanssonDev
export MACOSX_DEPLOYMENT_TARGET=10.11
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -arch x86_64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk -L/Users/corrychapman/Library/Developer/Xcode/DerivedData/JanssonDev-dispcmnteuwiedaiazlbkwtztfcu/Build/Products/Debug -L/usr/local/lib -L/Users/corrychapman/Desktop/jansson-2.11/JanssonDev -F/Users/corrychapman/Library/Developer/Xcode/DerivedData/JanssonDev-dispcmnteuwiedaiazlbkwtztfcu/Build/Products/Debug -filelist /Users/corrychapman/Library/Developer/Xcode/DerivedData/JanssonDev-dispcmnteuwiedaiazlbkwtztfcu/Build/Intermediates/JanssonDev.build/Debug/JanssonDev.build/Objects-normal/x86_64/JanssonDev.LinkFileList -mmacosx-version-min=10.11 -Xlinker -no_deduplicate -Xlinker -dependency_info -Xlinker /Users/corrychapman/Library/Developer/Xcode/DerivedData/JanssonDev-dispcmnteuwiedaiazlbkwtztfcu/Build/Intermediates/JanssonDev.build/Debug/JanssonDev.build/Objects-normal/x86_64/JanssonDev_dependency_info.dat -o /Users/corrychapman/Library/Developer/Xcode/DerivedData/JanssonDev-dispcmnteuwiedaiazlbkwtztfcu/Build/Products/Debug/JanssonDev
Undefined symbols for architecture x86_64:
"_json_array_get", referenced from:
_main in main.o
"_json_array_size", referenced from:
_main in main.o
"_json_delete", referenced from:
_json_decref in main.o
"_json_loads", referenced from:
_main in main.o
"_json_object_get", referenced from:
_main in main.o
"_json_string_value", referenced from:
_main in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Found it. Build Settings -> Linking -> Other Linker Flags: -ljansson
I am trying to use the hdf5-format to store data. Problem is, that I fail to link against the library. I have the following code
#include <H5Cpp.h>
int main(void){
H5::H5File file("test_MatrixRoundTrip_Double.h5", H5F_ACC_TRUNC);
}
and compile it using
gcc -std=c++11 -o main main.cpp -I /usr/local/include/ -L /usr/local/lib/ -lhdf5 -lhdf5_hl
This always returns the error
Undefined symbols for architecture x86_64:
"H5::FileAccPropList::DEFAULT", referenced from:
_main in main-c207d1.o
"H5::FileCreatPropList::DEFAULT", referenced from:
_main in main-c207d1.o
"H5::H5File::H5File(char const*, unsigned int, H5::FileCreatPropList const&, H5::FileAccPropList const&)", referenced from:
_main in main-c207d1.o
"H5::H5File::~H5File()", referenced from:
_main in main-c207d1.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
I installed the hdf5 library on OSX using
brew install homebrew/science/hdf5
What am I doing wrong here?
You are including the HDF5 C++ header file, but only linking the HDF5 C library. Add the line: -lhdf5_cpp to link the C++ shared object and use locate libhdf5_cpp to find it's libpath.
I'm trying to compile something I've fetched off of github with gcc:
users-MBP:Chip-8-Emulator user$ gcc -o chip8 chip8.c
Undefined symbols for architecture x86_64:
"_SDL_Delay", referenced from:
_chip8_draw in chip8-bc89fc.o
"_SDL_Flip", referenced from:
_chip8_draw in chip8-bc89fc.o
"_SDL_GetKeyState", referenced from:
_chip8_execute in chip8-bc89fc.o
_chip8_prec in chip8-bc89fc.o
"_SDL_GetVideoSurface", referenced from:
_chip8_draw in chip8-bc89fc.o
"_SDL_Init", referenced from:
_chip8_prepare in chip8-bc89fc.o
"_SDL_LockSurface", referenced from:
_chip8_draw in chip8-bc89fc.o
"_SDL_PollEvent", referenced from:
_chip8_prepare in chip8-bc89fc.o
_chip8_prec in chip8-bc89fc.o
"_SDL_SetVideoMode", referenced from:
_chip8_prepare in chip8-bc89fc.o
"_SDL_UnlockSurface", referenced from:
_chip8_draw in chip8-bc89fc.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
The error seems to be an issue with the SDL library in this case, but I've had the exact same issue with several other little projects I treid to compile. Before compiling, I installed the SDL libs and checked they are there:
users-MBP:Chip-8-Emulator user$ ls /usr/local/lib/
...
libSDL-1.2.0.dylib
libSDL.a
libSDL.dylib
libSDLmain.a
...
After lots of Googling it seems I'm not the only one with this problem and I couldn't find solution that worked. It seems that osx doesn't include /use/local/lib in the default linker paths.
How can I fix this (a permanent solution would be welcome)?
EDIT
Following a suggestion from user Alex I tried with $ gcc -o chip8 -L/usr/local/lib chip8.c. The error and output is identical to the above.
You'll want to add -L/usr/local/lib -lSDL to your GCC invocation.
As for a more permanent solution, this is a convention of OS X, and strictly speaking /usr/local/lib is a non-standard installation location.
I am trying to compile a mex file that I wrote in order to run a pre-existing C program in MATLAB. I am getting the following errors:
>> mex src/main.c -Iinclude -I/Users/my_name/mpfr-3.1.1/src/ -I/Users/my_name/gmp-5.0.5 -Lsrc0 -output cpdetect_c
Undefined symbols for architecture x86_64:
"_binomial_main", referenced from:
_cpdetect in main.o
"_gaussian1_main", referenced from:
_cpdetect in main.o
"_gaussianU_main", referenced from:
_cpdetect in main.o
"_mpfr_clears", referenced from:
_cpdetect in main.o
"_mpfr_exp10", referenced from:
_cpdetect in main.o
"_mpfr_inits2", referenced from:
_cpdetect in main.o
"_mpfr_set_d", referenced from:
_cpdetect in main.o
"_poisson_main", referenced from:
_cpdetect in main.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
I am confused because these functions are all part of files that I #Include in my code. How do I get the compiler to find them?
I am running MATLAB R2013a on Mac OS X 10.8 with Xcode version 4.6.3.
Thanks for any advice!
UPDATE1:
#Shai: Contents of my src0 folder:
>> ls src0
Makefile gaussian1.o test_gaussian1.c test_tools.c
Makefile.am loadtraj.c test_gaussian1_point_calc.c test_tools.o
Makefile.in loadtraj.o test_load tools.c
binomial.c main.c test_load.c tools.o
binomial.o main.o test_load.o
cpdetect poisson.c test_poisson.c
gaussian1.c poisson.o test_tools
This C program (originally meant to run on the command line) came from a friend and already had the src0 folder present. I modified the code files in the 'src' folder when writing the mex function, but I didn't touch the src0 folder.
UPDATE 2:
I realized I was pointing to the wrong location for mpfr. I am now using the following compile command:
>> mex src/main.c src/binomial.c src/gaussian1.c src/gaussianU.c src/poisson.c -Iinclude -I/usr/local/include -lmpfr -output cpdetect_c
and it is giving the following errors:
Undefined symbols for architecture x86_64:
"_mpfr_mul_d", referenced from:
_gaussian1_calc_constant_part in gaussian1.o
_gaussianU_calc_constant_part in gaussianU.o
"_mpfr_printf", referenced from:
_find_gaussian1_change_point in gaussian1.o
_gaussian1_point_calc in gaussian1.o
_gaussianU_calc_constant_part in gaussianU.o
_find_gaussianU_change_point in gaussianU.o
_find_poisson_change_point in poisson.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
mex: link of ' "cpdetect_c.mexmaci64"' failed.
This is strange. It's not like the compiler can't find any of the mpfr functions - there are lots of others that it seems to be finding without any trouble (and if I deliberately omit the -lmpfr flag, I get a much longer list of undefined symbols). I did confirm that mpfr_mul_d and mpfr_printf are part of the mpfr distribution I installed. Any ideas? Thanks.
The answer was provided by Amro - it is necessary to both point to the location of the library (using the flag -L/usr/local/lib in this case) and to tell the compiler to link to it (using the flag -lmpfr). Thanks also to Shai for help troubleshooting this.
Trying to compile the example hello_world.c from the zeromq tutorial:
http://zguide.zeromq.org/page:all#Ask-and-Ye-Shall-Receive
Pretty sure I have everything installed in OSX Mountain Lion.
clang -Wall hwserver.c -o hwserver
gives me an error:
Undefined symbols for architecture x86_64:
"_zmq_bind", referenced from:
_main in hwserver-OgrEe6.o
"_zmq_ctx_new", referenced from:
_main in hwserver-OgrEe6.o
"_zmq_msg_close", referenced from:
_main in hwserver-OgrEe6.o
"_zmq_msg_data", referenced from:
_main in hwserver-OgrEe6.o
"_zmq_msg_init", referenced from:
_main in hwserver-OgrEe6.o
"_zmq_msg_init_size", referenced from:
_main in hwserver-OgrEe6.o
"_zmq_msg_recv", referenced from:
_main in hwserver-OgrEe6.o
"_zmq_msg_send", referenced from:
_main in hwserver-OgrEe6.o
"_zmq_socket", referenced from:
_main in hwserver-OgrEe6.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
I'm not the most experienced in C. Not sure if I sure be adding a compiler flag for the zmq dylib or headers or my $PATH being off.
in /usr/local/lib:
libzmq.3.dylib
libzmq.a
libzmq.dylib
libzmq.la
and in /usr/local/include:
zmq.h
zmq_utils.h
and echo $PATH:
/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/local/lib/:/usr/local/include/
You list the ZeroMQ libraries in your question, but you do not actually link with them. Change the command line to this:
clang -Wall hwserver.c -o hwserver -L/usr/local/lib -lzmq
Explanation of the extra arguments:
-L/usr/local/lib tells the linker to add a path (/usr/local/lib) to the library search path.
-lzmq tells the library to link with the zmq library.
The $PATH environment variable have nothing to do with this, it just tells the shell where to look for commands.