I am trying to compile my program on my new server, but it's not working for me at the moment.
Error log is:
rasmus#web01:~/c++$ make test
g++ `mysql_config --cflags --libs` main.cpp logger.cpp cpulogger.cpp -o test
/tmp/ccPaMZUy.o: In function `CPULogger':
/home/rasmus/c++/cpulogger.cpp:7: undefined reference to `mysql_init'
/home/rasmus/c++/cpulogger.cpp:8: undefined reference to `mysql_real_connect'
/home/rasmus/c++/cpulogger.cpp:10: undefined reference to `mysql_get_client_info'
/tmp/ccPaMZUy.o: In function `~CPULogger':
/home/rasmus/c++/cpulogger.cpp:16: undefined reference to `mysql_close'
collect2: ld returned 1 exit status
make: *** [all] Error 1
As you can see I am compiling against MySQL - I have checked that mysql.h is present in include paths.
What am I missing?
cpulogger.cpp has #include "cpulogger.h" at the top, then cpulogger.h has this:
#include <iostream>
#include <fstream>
#include <mysql/mysql.h>
The compiler does not complain about missing mysql/mysql.h, so that part must work?
Output of mysql_config:
rasmus#web01:~/c++$ mysql_config --cflags --libs
-I/usr/include/mysql -DBIG_JOINS=1 -fno-strict-aliasing -g
-L/usr/lib -lmysqlclient -lpthread -lz -lm -lrt -ldl
Makefile:
all:
g++ `mysql_config --cflags --libs` main.cpp logger.cpp cpulogger.cpp -o test
test: all
./test
It's a fresh Ubuntu server installation with a mysql-server install on it.
[solved]:
Putting linker libraries at the end of the compiler commands works.
all:
g++ main.cpp logger.cpp cpulogger.cpp -o test `mysql_config --cflags --libs`
See answer below for explanation.
The order of arguments to the linker is significant. Use mysql-config after listing the files that need it. The linker will see that cpulogger.o needs mysql_init and look in libraries listed after it for the symbol. If the libraries were listed earlier in the arguments they won't be searched again.
Related
I am trying to run the code from this Website: https://quuxplusone.github.io/blog/2020/01/26/openssl-part-3/
but i get the following error message
C:/Strawberry/c/bin/../lib/gcc/x86_64-w64-mingw32/8.3.0/../../../../x86_64-w64-mingw32/bin/ld.exe: cannot find -lssl -lcrypto
collect2.exe: error: ld returned 1 exit status
I dont know what is the problem, since when i use
gcc -o client clientserv.cpp -lssl -lcrypto
to Compile other code it works fine but using the command from the website doesnt work.
Edit:
The command used on the website is
g++ -std=c++14 clientserv.cpp $(pkg-config --cflags --libs openssl) -o https-server
So it seems that the proper command to run it on windows is
g++ -std=c++14 clientserv.cpp -lssl -lcrypto -o https-server
When using gcc instead it has some Problems, which led me to believe i have some configuration problem
I've installed the libglfw3-dev:amd64 package on Ubuntu using the standard sudo apt get etc. My following compiling line is:
g++ -o output -IL/usr/lib/x86_64-linux-gnu -lglfw driver.o
My current c++ file is:
#include <GLFW/glfw3.h>
int main(void)
{
GLFWwindow* window;
if (!glfwInit())
return -1;
}
I've tried using local libraries of glfw and setting the -I and -L locations but nothing has seemed to work. I've made sure the .so and .h files are in their respective locations but I always get this error while running make:
g++ -o output -I/usr/include/GLFW -L/usr/lib/x86_64-linux-gnu -lglfw
driver.o
driver.o: In function `main':
driver.cpp:(.text+0x5): undefined reference to `glfwInit'
collect2: error: ld returned 1 exit status
Makefile:2: recipe for target 'output' failed
make: *** [output] Error 1
I've tried looking at all the other SO posts and they recommend compiling with tons of extra flags, but the only thing I've been able to draw from them is that something is wrong with my library since VScode detects the .h files. How can I compile this without any errors?
Have you tried swapping the linker arguments around? That is, compile with
g++ -o output driver.o -lglfw
The linker goes through the files from left to right, and it has to know which symbols from libraries you need, before the libraries are processed.
All is perfectly explained in the manual https://www.glfw.org/docs/latest/build_guide.html#build_link_pkgconfig
The key problem is in your -I/usr/include/GLFW and #include <GLFW/glfw3.h> that gives in sum the path /usr/include/GLFW/GLFW/glfw3.h. I suppose this is a wrong path to glfw3.h. compilation was successful because of the system default include path -I/usr/include.
Do not tune compiler flags manually, let pkg-config do
it for you.
A typical compile and link command-line when using the static version of the GLFW library may look like this:
g++ -o output `pkg-config --cflags glfw3` yourprog.c `pkg-config --static --libs glfw3`
If you are using the shared version of the GLFW library, simply omit the --static flag.
g++ -o output `pkg-config --cflags glfw3` yourprog.c `pkg-config --libs glfw3`
When I compile my code that uses OpenCV and caffe, I get the following linker errors:
../libs/libopencv_highgui.so: undefined reference to `g_mutex_lock'
../libs/libgstbase-0.10.so.0: undefined reference to `g_cond_init'
../libs/libopencv_highgui.so: undefined reference to `g_mutex_unlock'
../libs/libopencv_highgui.so: undefined reference to `g_cond_broadcast'
../libs/libgstreamer-0.10.so.0: undefined reference to `g_cond_wait_until'
../libs/libopencv_highgui.so: undefined reference to `g_mutex_new'
...
collect2: ld returned 1 exit status
This my g+ commmand:
g++ -DCPU_ONLY=1 test.cpp -o test -I../include -I../include/openblas -L../libs
-Wl,-rpath=../libs -lcaffe -lglog -lboost_system -lopencv_core -lopencv_highgui
-lopencv_imgproc
What am I missing?
Yep, this is a simple case of not linking against glib.
In general, to fix this kind of thing, google one of the symbol names(g_mutex_lock, for example) to figure out what library it comes from. In this case, it is glib. Then, look in their documentation for help compiling applications that use their library(if you can't figure it out on your own). In this case, you end up here.
Once you have made sure you have all required packages installed, you augment your compiler options as needed.
In your case, try g++ -DCPU_ONLY=1 test.cpp -o test `pkg-config --cflags glib-2.0` -I../include -I../include/openblas `pkconfig --libs glib-2.0` -L../libs -Wl,-rpath=../libs -lcaffe -lglog -lboost_system -lopencv_core -lopencv_highgui -lopencv_imgproc
Note the use of pkg-config. For reference, compiling a sample application that uses only glib might look like this: gcc hello.c `pkg-config --cflags --libs glib-2.0`
I'm trying to compile this (also listed in the mysql c++ connector documentation): http://pastebin.com/HLv4zR0r
But I get these errors: http://pastebin.com/3t0UbeFy
This is how I tried compiling:
g++ -o test test.cpp `mysql_config --cflags --libs` -I./include/cppconn -L./lib -lmysqlcppconn-static
The result of running mysql_config --cflags --libs is:
-I/usr/include/mysql -DBIG_JOINS=1 -fno-strict-aliasing -g
-L/usr/lib/x86_64-linux-gnu -lmysqlclient -lpthread -lz -lm -lrt -ldl
Edit:
After running Jonathan Wakely's suggested command with properly-ordered linker arguments,
g++ -o test test.cpp -I./include/cppconn -L./lib -lmysqlcppconn-static `mysql_config --cflags --libs`
I get different errors: http://pastebin.com/4EWNgy9i
The mysqlcppcon library depends on the mysqlclient C libraries, so you need to put the mysqlclient libs after -lmysqlcppconn-static
g++ -o test test.cpp -I./include/cppconn -L./lib -lmysqlcppconn-static `mysql_config --cflags --libs`
The order of linker arguments matters. The linker looks at each file in order and decides if it needs any symbols from it. By the time it sees the libmysqlcppconn-static.a file it has already looked at (and ignored) the libmysqlclient.so library, and doesn't go back to look at it again.
I've worked with opencv on linux in the past, but not with cuda. I've struggled with the following compilation error for months. And after trying many solutions i gave up and worked with windows. However, i really want to work on linux. This is the command i'm using to compile the threshold example given on the opencv_gpu website.
nvcc `pkg-config --libs opencv` -L. -L/usr/local/cuda/lib -lcuda -lcudart `pkg-config --cflags opencv` -I. -I/usr/local/cuda/include threshold.cpp -o threshold
here is the error:
/tmp/tmpxft_0000171b_00000000-1_threshold.o: In function `main':
threshold.cpp:(.text+0x124): undefined reference to `cv::gpu::Stream::Null()'
threshold.cpp:(.text+0x156): undefined reference to `cv::gpu::threshold(cv::gpu::GpuMat const&, cv::gpu::GpuMat&, double, double, int, cv::gpu::Stream&)'
threshold.cpp:(.text+0x16d): undefined reference to `cv::gpu::GpuMat::download(cv::Mat&) const'
/tmp/tmpxft_0000171b_00000000-1_threshold.o: In function `cv::gpu::GpuMat::GpuMat(cv::Mat const&)':
threshold.cpp:(.text._ZN2cv3gpu6GpuMatC1ERKNS_3MatE[cv::gpu::GpuMat::GpuMat(cv::Mat const&)]+0x63): undefined reference to `cv::gpu::GpuMat::upload(cv::Mat const&)'
/tmp/tmpxft_0000171b_00000000-1_threshold.o: In function `cv::gpu::GpuMat::~GpuMat()':
threshold.cpp:(.text._ZN2cv3gpu6GpuMatD1Ev[cv::gpu::GpuMat::~GpuMat()]+0xd): undefined reference to `cv::gpu::GpuMat::release()'
collect2: ld returned 1 exit status
make: *** [all] Error 1
In order to help you I had to download and install CUDA 4.0 (with driver 4.0.21) and then download and compiled OpenCV 2.3 for my Macbook Pro, on Mac OS X 10.6.8.
The sample code from OpenCV_GPU was successfully compiled on my machine through:
g++ threshold.cpp -o threshold `pkg-config --cflags --libs opencv` -lopencv_gpu
You were missing the flag -lopencv_gpu , which is not included by pkg-config.
This looks like a linker problem. I don't know, if nvcc follows the same conventions as gcc, but I would try:
nvcc `pkg-config --cflags opencv` -L. -L/usr/local/cuda/lib -I. -I/usr/local/cuda/include -o threshold threshold.cpp `pkg-config --libs opencv` -lcuda -lcudart
More in general: If you write
gcc t.cpp -lB -lA
it means that libB depends on symbols from libA; t.cpp can depend on symbols from libA and libB.
Instead of using pkg-config in the nvcc line I would suggest just manually pointing the compiler at the opencv library and include files. Perhaps you could just run pkg-config --libs opencv on the command line and copy the necessary libs into your nvcc command. It seems nvcc is only choking on the opencv libs (it can't find them for sure!).