I've been trying to set up (Install and get the correct libraries) for my computer so I could start graphic programming.
I've visited the OpenGL site, and have found it unhelpful.
I tried the Wikibooks' Setting up page, but that has install info specific to Debian and Debian like systems and I couldn't find the corresponding stuff for fedora.
I know C and python and would prefer to work in C if possible, I did find PyOpenGL.noarch and installed it using yum.
I looked up a couple of other sites and didn't find much but I managed to Install freeglut-devel
I checked and found the GL libraries in /usr/include/GL folder but when I try to run the following code{taken from the wikibooks site itself, so I'm assuming it works}:
#include <stdio.h> /* printf */
#include <GL/glut.h> /* glut graphics library */
/*
* Linux c console program
* gcc f.c -lglut
* ./a.out
* */
main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutCreateWindow("red 3D lighted cube");
printf("GL_VERSION = %s\n",glGetString(GL_VERSION) ); /* GL_VERSION = 2.1.2 NVIDIA 195.36.24 */
return 0;
}
And when I do gcc -lglut filename.c
I get the following errors:
/usr/bin/ld: /usr/lib/gcc/i686-redhat-linux/4.6.1/../../../libglut.so: undefined reference to symbol 'glGetString'
/usr/bin/ld: note: 'glGetString' is defined in DSO /usr/lib/libGL.so.1 so try adding it to the linker command line
/usr/lib/libGL.so.1: could not read symbols: Invalid operation
collect2: ld returned 1 exit status
And I have no Idea what to do.
A basic step-by-step procedure would be much appreciated but if any help is always welcome.
Try adding -lGL to the command line you use to compile it (that's what the error message is telling you to do).
This question also suggests that you'll need -lGLU as well.
Additionally, I would put the libraries after the source files that use them, so:
gcc filename.c -lglut -lGL -lGLU
Instead of:
gcc -lglut -lGL -lGLU filename.c
There is some more information about why you get this message on fedora here, but the basic fix is to explicitly link the missing library.
Related
Is it possible (and how) to use MinGW-w64 for building of C-extensions for Python or embeding Python on Windows?
Let's take as example the following cython-extension foo.pyx:
print("foo loaded")
from which the C-code can be generated either via cython -3 foo.pyx or cython -3 --embed foo.pyx if interpreter should be embedded.
While mingw-w64-compiler is not really supported (the only supported windows compiler is MSVC), it can be used to create C-extensions or to embed Python. There are however no guarantee, this won't break in the future versions.
distutils does not support mingw-w64, so there is no gain in setting up a setup.py-file - the steps must be performed manually.
First we need some information usually provided by distutils:
Headers: We need the path to the Python includes. For a way to find them see this SO-post.
DLL: mingw-w64's linker works differently than MSVC's: python-dll and not python-lib is needed. So we need the path to the pythonXY.dll which is usually next the the python.exe.
Once the C-code is created/generated, the extension can be build via
x86_64-w64-mingw32-gcc -shared foo.c -DMS_WIN64 -O2 <other_options> -I <path_to_python_include> -L <path_to_python_dll> -lpython37 -o foo.pyd
The important details are:
it is probably Ok to use only use -O2 for optimization and leave <other_options> empty-
It is important to define MS_WIN64-macro (e.g. via -DMS_WIN64). In order to build for x64 on windows it must be set, but it works out of the box only for MSVC (defining _WIN64 could have slightly different outcomes):
#ifdef _WIN64
#define MS_WIN64
#endif
if it is not done, at least for files generated by Cython the following error message will be generated by the compiler:
error: enumerator value for ‘__pyx_check_sizeof_voidp’ is not an integer constant
201 | enum { __pyx_check_sizeof_voidp = 1 / (int)(SIZEOF_VOID_P == sizeof(void*)) };
pyd is just a dll in disguise, thus we need the -shared option, which means a dynamic library (i.e. shared-object in Linux-world) will be created.
It is important, that the python-library (pythonXY) should be the dll itself and not the lib (see this SO-post). Thua we use the path to pythonXY.dll (in my case python37) and not pythonXY.lib, as it would be the case for MSVC.
One probably should add the proper suffix to the resulting pyd-file, I use the old convention for simplicity here.
Embeded Python:
In this case an executable should be build (e.g. the C-file is generated by Cython with --embed option: cython -3 --embed foo.pyx) and thus the command line looks as follows:
x86_64-w64-mingw32-gcc foo.c -DMS_WIN64 -O2 <other_options> -I <path_to_python_include> -L <path_to_python_dll> -lpython37 -o foo.exe -municode
There are two important differences:
-shared should no longer be used, as the result is no longer a dynamic library (that is what *.pyd-file is after all) but an executable.
-municode is needed, because for Windows, Cython defines int wmain(int argc, wchar_t **argv) instead of int main(int argc, char** argv). Without this option, an error message like
/build/mingw-w64-_1w3Xm/mingw-w64-4.0.4/mingw-w64-crt/crt/crt0_c.c:18: undefined reference to 'WinMain'
collect2: error: ld returned 1 exit status
would appear (see this SO-post for more information).
Note: for the resulting executable to run, a whole python-distribution (and not only the dll) is needed (see also this SO-post), otherwise the resulting executable will abort with error (either the python dll wasn't found or the python installation or the site packages - depending on the configuration of the machine on which the exe has to run).
mingw-w64 can also be used on Linux for cross-compilation for Windows, see this SO-post.
Is it possible (and how) to use MinGW-w64 for building of C-extensions for Python or embeding Python on Windows?
Let's take as example the following cython-extension foo.pyx:
print("foo loaded")
from which the C-code can be generated either via cython -3 foo.pyx or cython -3 --embed foo.pyx if interpreter should be embedded.
While mingw-w64-compiler is not really supported (the only supported windows compiler is MSVC), it can be used to create C-extensions or to embed Python. There are however no guarantee, this won't break in the future versions.
distutils does not support mingw-w64, so there is no gain in setting up a setup.py-file - the steps must be performed manually.
First we need some information usually provided by distutils:
Headers: We need the path to the Python includes. For a way to find them see this SO-post.
DLL: mingw-w64's linker works differently than MSVC's: python-dll and not python-lib is needed. So we need the path to the pythonXY.dll which is usually next the the python.exe.
Once the C-code is created/generated, the extension can be build via
x86_64-w64-mingw32-gcc -shared foo.c -DMS_WIN64 -O2 <other_options> -I <path_to_python_include> -L <path_to_python_dll> -lpython37 -o foo.pyd
The important details are:
it is probably Ok to use only use -O2 for optimization and leave <other_options> empty-
It is important to define MS_WIN64-macro (e.g. via -DMS_WIN64). In order to build for x64 on windows it must be set, but it works out of the box only for MSVC (defining _WIN64 could have slightly different outcomes):
#ifdef _WIN64
#define MS_WIN64
#endif
if it is not done, at least for files generated by Cython the following error message will be generated by the compiler:
error: enumerator value for ‘__pyx_check_sizeof_voidp’ is not an integer constant
201 | enum { __pyx_check_sizeof_voidp = 1 / (int)(SIZEOF_VOID_P == sizeof(void*)) };
pyd is just a dll in disguise, thus we need the -shared option, which means a dynamic library (i.e. shared-object in Linux-world) will be created.
It is important, that the python-library (pythonXY) should be the dll itself and not the lib (see this SO-post). Thua we use the path to pythonXY.dll (in my case python37) and not pythonXY.lib, as it would be the case for MSVC.
One probably should add the proper suffix to the resulting pyd-file, I use the old convention for simplicity here.
Embeded Python:
In this case an executable should be build (e.g. the C-file is generated by Cython with --embed option: cython -3 --embed foo.pyx) and thus the command line looks as follows:
x86_64-w64-mingw32-gcc foo.c -DMS_WIN64 -O2 <other_options> -I <path_to_python_include> -L <path_to_python_dll> -lpython37 -o foo.exe -municode
There are two important differences:
-shared should no longer be used, as the result is no longer a dynamic library (that is what *.pyd-file is after all) but an executable.
-municode is needed, because for Windows, Cython defines int wmain(int argc, wchar_t **argv) instead of int main(int argc, char** argv). Without this option, an error message like
/build/mingw-w64-_1w3Xm/mingw-w64-4.0.4/mingw-w64-crt/crt/crt0_c.c:18: undefined reference to 'WinMain'
collect2: error: ld returned 1 exit status
would appear (see this SO-post for more information).
Note: for the resulting executable to run, a whole python-distribution (and not only the dll) is needed (see also this SO-post), otherwise the resulting executable will abort with error (either the python dll wasn't found or the python installation or the site packages - depending on the configuration of the machine on which the exe has to run).
mingw-w64 can also be used on Linux for cross-compilation for Windows, see this SO-post.
I'm have a C++ program that is pretty far developed to do it's own job and now we'd like to add an addition functionality to it and we thought that making said functionality in Python and then calling that python with required inputs from the C++ when needed would be the best way to go as it keeps them separated and allows us to use this python script from elsewhere too.
As a first step I decided to try to make a test program to see how this would work and seems like it was a good idea because I can't get it to work.
How do I run separate python from c++?
I have tried following this guide and while it seems good it doesn't give any information on what compiler options should I run this with?
I have two files, cpp.cpp and python.py
This is my cpp.cpp file:
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <ncurses.h>
#include <Python.h>
using namespace std;
int main() {
std::cout << "C++ program started!\n";
char filename[] = "python.py";
FILE* fp;
Py_Initialize();
fp = _Py_fopen(filename, "r");
PyRun_SimpleFile(fp, filename);
Py_Finalize();
std::cout << "C++ program is ending!\n";
return 0;
}
and my python file is just two printf line:
#print('External Python program running...')
#print('Hello World from Python program')
I then try to compile this, give it all the includes it seems to want and then execute the output file:
g++ -I . -I /home/ahomm/python3.6/Include -I /home/ahomm/python3.6/release cpp.cpp && ./a.out
This is the output I get:
/tmp/cccQsh1p.o: In function `main':
cpp.cpp:(.text+0x3f): undefined reference to `Py_Initialize'
cpp.cpp:(.text+0x52): undefined reference to `_Py_fopen'
cpp.cpp:(.text+0x70): undefined reference to `PyRun_SimpleFileExFlags'
cpp.cpp:(.text+0x75): undefined reference to `Py_Finalize'
collect2: error: ld returned 1 exit status
What am I missing? is just something just a little or completely wrong?
cpp and py files and located in the same directory.
And how do I then read the output of python in C++? Haven't even got to that yet...
You have to link your code with libpython3.x.a/python3.x.lib (x - version of python you use). Which file to link: *.a or *.lib depends of your OS. The files are available with python distribution.
Here is a code with cmake that works for me:
cmake_minimum_required(VERSION 2.8.9)
project (embpy)
add_executable(embpy embpy.cpp)
target_include_directories(embpy PRIVATE /path-to-python/Python38/include/python3.8)
target_link_libraries(embpy /path-to-python/Python38/lib/libpython3.8.a)
the embpy.cpp is the same as yours
Figured it out myself then, the problem was incomplete compiler arguments.
This is what I got it to works with:
g++ -fPIC $(python3.6-config --cflags) cpp.cpp $(python3.6-config --ldflags)
the key missing parts were $(python3.6-config --cflags) before and $(python3.6-config --ldflags) after the file that was to be compiled. The first one gives g++ the compile options and the latter gives the flags for linking.
Found the solution from python docs, part 1.6.
I'm doing some trials to embed python in a c program.
I use CMake 2.8.12.2 and gcc 4.8.1 to build the application. My Python version is 2.7.11. Running on W7.
This is how I'm linking the libraries in the CMakeLists.txt, which has always worked for me before with static libraries:
CMakeLists.txt
cmake_minimum_required(VERSION 2.7 FATAL_ERROR)
project(testpy)
include_directories("C:\\Anaconda\\include")
link_directories("C:\\Anaconda\\libs")
set(CMAKE_BUILD_TYPE Release)
set(SOURCE_FILES testpy.c)
add_executable(testpy ${SOURCE_FILES} Python.h)
set(PYLIB_DIR "C:\\Anaconda\\libs")
message(${PYLIB_DIR})
find_library(PYlib python27.lib HINTS ${PYLIB_DIR})
include_directories(${PYLIB_DIR})
message(${PYlib})
TARGET_LINK_LIBRARIES(testpy ${PYlib})
testpy.c
#include <Python.h>
int main(int argc, char *argv[])
{
Py_Initialize();
PyRun_SimpleString("from time import time,ctime\nprint('Today is',ctime(time())\n)");
Py_Finalize();
return 0;
}
The errors I am getting when making:
CMakeFiles\testpy.dir/objects.a(testpy.c.obj):testpy.c:(.text.startup+0x10): und
efined reference to `_imp__Py_Initialize'
CMakeFiles\testpy.dir/objects.a(testpy.c.obj):testpy.c:(.text.startup+0x25): und
efined reference to `_imp__PyRun_SimpleStringFlags'
c:/mingw/bin/../lib/gcc/mingw32/4.8.1/../../../../mingw32/bin/ld.exe: CMakeFiles
\testpy.dir/objects.a(testpy.c.obj): bad reloc address 0x25 in section `.text.st
artup'
c:/mingw/bin/../lib/gcc/mingw32/4.8.1/../../../../mingw32/bin/ld.exe: final link
failed: Invalid operation
collect2.exe: error: ld returned 1 exit status
CMakeFiles\testpy.dir\build.make:90: recipe for target 'testpy.exe' failed
mingw32-make[2]: *** [testpy.exe] Error 1
CMakeFiles\Makefile2:62: recipe for target 'CMakeFiles/testpy.dir/all' failed
mingw32-make[1]: *** [CMakeFiles/testpy.dir/all] Error 2
Makefile:74: recipe for target 'all' failed
mingw32-make: *** [all] Error 2
I'm pretty shure is a linking problem, but I still not seing where it is, and how to fix it. Seen and tried also a lot of solutions suggested here and in other forums without success.
In both \include and \libs folders can be found the python.h and the python27.lib, respectively.
Thanks in advance for your feedback.
I am trying to compile a simple C extension in Mac to use with Python, and all works well in the command line. Code and gcc command that works are presented below.
Now I am trying to build the same extension in Xcode 4.5 (Mac OS10.8), and I tried several target settings for either dylib or static library, but I always get a file that cannot be loaded in Python showing the error:
./myModule.so: unknown file type, first eight bytes: 0x21 0x3C 0x61 0x72 0x63 0x68 0x3E 0x0A
My ultimate target is to create a workspace in XCode with the source code of a C/C++ extension and have python script that calls it in Xcode. So, if I need to debug the C/C++ extension I have XCode debugging capabilities. I am aware that XCode do not debug into Python script, but it can run it, correct ?
gcc -shared -arch i386 -arch x86_64 -L/usr/lib/python2.7 -framework python -I/usr/include/python2.7 -o myModule.so myModule.c -v
#include <Python.h>
/*
* Function to be called from Python
*/
static PyObject* py_myFunction(PyObject* self, PyObject* args)
{
char *s = "Hello from C!";
return Py_BuildValue("s", s);
}
/*
* Another function to be called from Python
*/
static PyObject* py_myOtherFunction(PyObject* self, PyObject* args)
{
double x, y;
PyArg_ParseTuple(args, "dd", &x, &y);
return Py_BuildValue("d", x*y);
}
/*
* Bind Python function names to our C functions
*/
static PyMethodDef myModule_methods[] = {
{"myFunction", py_myFunction, METH_VARARGS},
{"myOtherFunction", py_myOtherFunction, METH_VARARGS},
{NULL, NULL}
};
/*
* Python calls this to let us initialize our module
*/
void initmyModule()
{
(void) Py_InitModule("myModule", myModule_methods);
}
This guy seems to be having the same problem.
I've figured out the problem. Even though I changed the setting in xcode to specify output type "dynamic library" or "bundle", xcode was ignoring the setting. Starting a new BSD dynamic library project solved the issues I was seeing. Thanks for the help!
I've had success debugging unit-tested C extensions in XCode 4.6 using setuptools, virtualenv, unittest and GDB as the debugger.
I use virtualenvwrapper to create a virtualenv for the project and then set ~/.virtualenvs/module_name/bin/python as the executable to debug.
The single argument to pass to the virtualenv python interpreter in the Run configuration is the path to your test.py.
I then set GDB rather than None as the debugger launching it automatically.
The last step is to pass "setup.py install" as the arguments to your build tool (~/.virtualenvs/module_name/bin/python) on your test target's External Build Tool Configuration pane. The virtualenv provides a fairly simple way for you to install the shared object for your C extension into the test script python interpreter's library path without actually installing it into the global site-packages for your host.
With this setup I can call the extension code from a python script (the ultimate aim) and still debug the C code using XCode's GUI debug support.
If I haven't described this clearly please let me know and I'll share an example project.