I am beginning to use the SDL library for the first time and I used the apt-get install to download it onto the windows subsystem (Ubuntu). When I make calls to functions from the SDL library and then run the makefile, I am presented with:
/home/display.c:13: undefined reference to `SDL_Init'
/home/display.c:14: undefined reference to `SDL_GetError'
/home/display.c:17: undefined reference to `SDL_CreateWindow'
/home/display.c:19: undefined reference to `SDL_GetError'
/home/display.c:22: undefined reference to `SDL_CreateRenderer'
/home/display.c:24: undefined reference to `SDL_GetError'
The makefile looks like:
gcc -Wall -Werror -Wextra -Wunused -std=gnu99 -g -O0 -Wpedantic -lpthread -lSDL2main -lSDL2
I believe the issue is in linking and that the compiler cannot find where SDL is. However, if this were the case, there should be an error stating that #include SDL2/SDL.h cannot be found. Could this be an installation issue or an issue with the way I link SDL in the makefile?
The order in which I was placing the flags was incorrect. The libraries should be after the .c and .h files.
Related
I'm working on a program in which I use PDCurses3.5 functions using i686-w64-mingw32-gcc.exe.
When I compile the program, I keep getting errors such as "undefined reference to 'COLS'", "undefined reference to 'lines'".
I have checked that <curses.h> header and the library package properly installed.
Here is my input line:
> i686-w64-mingw32-gcc.exe set.o read.o elements.o random.o
> -L../standard/test -lplotfit -lplotget -lgfortran -Wl,--subsystem,console -mwindows -o runtime/mingw/result -lm -static -lws2_32 -lpdcurses
And the first part of the error is:
../standard/bin/mingw/menu.o:menu.c:(.text+0xb): undefined reference to `COLS'
../standard/bin/mingw/menu.o:menu.c:(.text+0x16): undefined reference to `COLS'
../standard/bin/mingw/menu.o:menu.c:(.text+0x33): undefined reference to `LINES'
../standard/bin/mingw/menu.o:menu.c:(.text+0x47): undefined reference to `MOVE'
../standard/bin/mingw/menu.o:menu.c:(.text+0x74): undefined reference to `initscr'
...
It seems the program cannot refer to libpdcurses.a in its library file.
What am I doing wrong?
When you use -lpdcurses, the linker looks for libpdcurses.a in certain predefined locations, plus those specified via -L. But, by default, the library is built as pdcurses.a. To link it, you can directly specify its location; e.g.:
gcc -oprogname.exe progname.c pdcurses.a
or
gcc -oprog2.exe prog2.c /pdcurses/win32/pdcurses.a
Alternatively, you can rename the library to libpdcurses.a, and either copy it to a location in the existing search path, or use -L:
gcc -oprogname.exe progname.c -lpdcurses
or
gcc -oprog2.exe prog2.c -L/pdcurses/win32 -lpdcurses
I have a library which uses the log function from math.h. When I compile and package this library, I get no compilation errors, which is normal (I think).
Now when I try to use the library in an application, gcc gives me linker errors:
Compiling mytestlist using "mytestlist.o":
gcc mytestlist.o -I/student/cmpt332/pthreads -I. -std=c99 -Wall -pedantic -L. -L/student/cmpt332/pthreads/lib/linuxx86_64/ -llist -o mytestlist
./liblist.a(list_adders.o): In function `NodeCreate':
list_adders.c:(.text+0x343): undefined reference to `log'
./liblist.a(list_adders.o): In function `ListCreate':
list_adders.c:(.text+0x62f): undefined reference to `log'
./liblist.a(list_adders.o): In function `ListFree':
list_adders.c:(.text+0xdcc): undefined reference to `log'
list_adders.c:(.text+0xe55): undefined reference to `log'
list_adders.c:(.text+0xefb): undefined reference to `log'
./liblist.a(list_adders.o):list_adders.c:(.text+0xf96): more undefined references to `log' follow
collect2: error: ld returned 1 exit status
Makefile:47: recipe for target 'mytestlist' failed
make: *** [mytestlist] Error 1
Why is this happening? The only solution that works is that I have to supply the -lm option to gcc when I compile the program that uses the library (even though the program itself makes no use of math.h), however I find this cumbersome to do.
I've also tried supplying the -lm option when compiling the library, but when the application is compiled using the library, I get the same linker errors.
Is there a way to compile the library with math.h without having to supply -lm to other programs that make use of the library?
In case you're wondering, I compile each object that makes up the library using:
gcc -std=c99 -Wall -pedantic -static -I. -c list_adders.c -o list_something.o -lm
And the library is packaged using:
ar cvfr liblist.a list_something.o ...
In your gcc -c command, the -lm isn't doing anything. It's a linker option, and -c means "don't link".
The proper place to put -lm is in fact after the -llist whenever you use it. That's how static library dependencies are done. Put it in the documentation for liblist.
If you want something fancier, there's pkg-config. With the appropriate configuration files, pkg-config --static --libs liblist will output -llist -lm.
(I am on Ubuntu) I am trying to run the PortAudio examples, but getting many errors (mentioned below). I have placed the header file portaudio.h in the directory of the program. I have no idea about it. I think it is linker error. Please help!
/tmp/cc5EbTlT.o: In function main':
paex_record.c:(.text+0x37e): undefined reference toPa_Initialize'
paex_record.c:(.text+0x397): undefined reference to Pa_GetDefaultInputDevice'
paex_record.c:(.text+0x3de): undefined reference toPa_GetDeviceInfo'
paex_record.c:(.text+0x436): undefined reference to Pa_OpenStream'
paex_record.c:(.text+0x45a): undefined reference toPa_StartStream'
paex_record.c:(.text+0x493): undefined reference to Pa_Sleep'
paex_record.c:(.text+0x4c2): undefined reference toPa_IsStreamActive'
paex_record.c:(.text+0x4eb): undefined reference to Pa_CloseStream'
paex_record.c:(.text+0x5fa): undefined reference toPa_GetDefaultOutputDevice'
paex_record.c:(.text+0x641): undefined reference to Pa_GetDeviceInfo'
paex_record.c:(.text+0x6b2): undefined reference toPa_OpenStream'
paex_record.c:(.text+0x6e3): undefined reference to Pa_StartStream'
paex_record.c:(.text+0x71c): undefined reference toPa_Sleep'
paex_record.c:(.text+0x728): undefined reference to Pa_IsStreamActive'
paex_record.c:(.text+0x74e): undefined reference toPa_CloseStream'
paex_record.c:(.text+0x77d): undefined reference to Pa_Terminate'
paex_record.c:(.text+0x7e5): undefined reference toPa_GetErrorText'
collect2: error: ld returned 1 exit status
Assuming you are compiling using gcc and you have a single C file foo.c, the compiler command would be
gcc -o foo foo.c -lrt -lasound -ljack -lpthread -lportaudio
The -l parameters are there to link the required libraries to your program, e.g. -lrt will link librt.a. The order does matter.
I got the required libraries from here: http://www.portaudio.com/docs/v19-doxydocs/compile_linux.html#comp_linux3. Don't know if they are correct. At least you need -lportaudio, obviously.
If the libraries are not found, you have to provide gcc a path, e.g.
gcc -L/usr/lib -o foo foo.c -lrt -lasound -ljack -lpthread -lportaudio
Regarding the header, you don't actually need to copy it into your program's directory. You'd rather include it as
#include <portaudio.h>
and add its directory to the include search path:
gcc -I/usr/include -L/usr/lib -o foo foo.c -lrt -lasound -ljack -lpthread -lportaudio
Of course, all this is better done in a Makefile.
I seem to be having an issue building the ethping executable. It cannot find any of the functions that are defined in pcap.h.
At first I thought it wasn't finding pcap.h, but I have checked the $PATH and /usr/include is there (the pcap.h there is a stub that then includes pcap/pcap.h, but that looks all good too).
I even tried -I /usr/include and -I /usr/include/pcap, but still no luck.
I have searched through tons of forum postings, but could not find a solution. So that's why I am here. Any ideas?
root:src# gcc -Wall -Werror -ggdb -g -O2 -lpcap -o ethping ethping.o ieee8021ag.o dot1ag_eth.o
ethping.o: In function `timeout_handler':
/home/ubuntu/Downloads/dot1ag-utils-master/src/ethping.c:65: undefined reference to `pcap_breakloop'
ethping.o: In function `main':
/home/ubuntu/Downloads/dot1ag-utils-master/src/ethping.c:183: undefined reference to `pcap_open_live'
/home/ubuntu/Downloads/dot1ag-utils-master/src/ethping.c:202: undefined reference to `pcap_compile'
/home/ubuntu/Downloads/dot1ag-utils-master/src/ethping.c:203: undefined reference to `pcap_setfilter'
/home/ubuntu/Downloads/dot1ag-utils-master/src/ethping.c:254: undefined reference to `pcap_next_ex'
/home/ubuntu/Downloads/dot1ag-utils-master/src/ethping.c:257: undefined reference to `pcap_perror'
collect2: error: ld returned 1 exit status
Similarly:
root:src# gcc -Wall -Werror -ggdb -g -O2 -lpcap -I /usr/include/pcap -o ethping ethping.o ieee8021ag.o dot1ag_eth.o
ethping.o: In function `timeout_handler':
/home/ubuntu/Downloads/dot1ag-utils-master/src/ethping.c:65: undefined reference to `pcap_breakloop'
ethping.o: In function `main':
/home/ubuntu/Downloads/dot1ag-utils-master/src/ethping.c:183: undefined reference to `pcap_open_live'
/home/ubuntu/Downloads/dot1ag-utils-master/src/ethping.c:202: undefined reference to `pcap_compile'
/home/ubuntu/Downloads/dot1ag-utils-master/src/ethping.c:203: undefined reference to `pcap_setfilter'
/home/ubuntu/Downloads/dot1ag-utils-master/src/ethping.c:254: undefined reference to `pcap_next_ex'
/home/ubuntu/Downloads/dot1ag-utils-master/src/ethping.c:257: undefined reference to `pcap_perror'
collect2: error: ld returned 1 exit status
root:src#
Changing the compile line fixed it. Placing -lpcap at the far right got it going as suggested.
gcc -Wall -Werror -ggdb -g -O2 -o ethping ethping.o ieee8021ag.o dot1ag_eth.o -lpcap
Either you are invoking the linker without the arguments to include the libpcap library, or the libraries are not installed. See http://www.tcpdump.org/ to obtain the library. Or if you are on a well-supported distribution, use the applicable install command:
sudo apt-get install libpcap-dev
or
sudo yum install libpcap-dev
I am trying to use Curl in C.
I visited Curl official page, and copied sample source code.
below is the link:
http://curl.haxx.se/libcurl/c/sepheaders.html
when I run this code with command "gcc test.c",
the console shows message like below.
/tmp/cc1vsivQ.o: In function `main':
test.c:(.text+0xe1): undefined reference to `curl_global_init'
test.c:(.text+0xe6): undefined reference to `curl_easy_init'
test.c:(.text+0x10c): undefined reference to `curl_easy_setopt'
test.c:(.text+0x12e): undefined reference to `curl_easy_setopt'
test.c:(.text+0x150): undefined reference to `curl_easy_setopt'
test.c:(.text+0x17e): undefined reference to `curl_easy_cleanup'
test.c:(.text+0x1b3): undefined reference to `curl_easy_cleanup'
test.c:(.text+0x1db): undefined reference to `curl_easy_setopt'
test.c:(.text+0x1e7): undefined reference to `curl_easy_perform'
test.c:(.text+0x1ff): undefined reference to `curl_easy_cleanup'
I do not know how to solve this.
You don't link with the library.
When using an external library you must link with it:
$ gcc test.c -lcurl
The last option tells GCC to link (-l) with the library curl.
In addition to Joachim Pileborg's answer, it is useful to remember that gcc/g++ linking is sensitive to order and that your linked libraries must follow the things that depend upon them.
$ gcc -lcurl test.c
will fail, missing the same symbols as before. I mention this because I came to this page for forgetting this fact.
I have the same problem, but i use g++ with a make file.
This is a linker issue.
You need to add option -lcurl on the compiler and on the linker.
In my case on the make file:
CC ?= gcc
CXX ?= g++
CXXFLAGS += -I ../src/ -I ./ -DLINUX -lcurl <- compile option
LDFLAGS += -lrt -lpthread -lcurl <- linker option
Gerard
Depending how bad things are you might need an -L/somewhere in LDFLAGS to let the linker know where the libraries are. ldconfig is supposed to pick them up and find them on every boot but on a new machine it can take a little prodding, like adding a directory to your /etc/ld.so.conf.