I'm working on embedding Python in some C++ code, but I'm getting stuck compiling it.
For a header file, I have
#include <Python.h>
I would initial try,
$g++ EmbeddedPython.cpp
but would end up getting
EmbeddedPython.cpp:1:20: error: Python.h: No such file or directory
EmbeddedPython.cpp: In function ‘int main(int, char**)’:
EmbeddedPython.cpp:6: error: ‘Py_Initialize’ was not declared in this scope
....
I then tried
g++ EmbeddedPython.cpp -I/System/Library/Frameworks/Python.framework/Versions/2.5/include/python2.5
and that got rid of the first two errors, but I still ended up with
Undefined symbols:
"_Py_Initialize", referenced from:
_main in ccxJAUAB.o
I'm a bit of new to this, but I think I'm learning fast. I believe I need to 'Link' a library, right? But which one and how? Do I need a dynamic or a static one?
I am working on a MacBook Pro.
You need to link against libpython. UNIX programmers do this with "-lpython" in the link command (ie at the end of that "g++" command). On a Mac, I think it would be "-framework Python".
Related
I have started learning C++ on Ubuntu. I am only a few months into using Linux as well.
I am attempting to port over a 2D Ball Collision Script from Javascript to C++ for learning purposes.
I am using simple2D for the drawing in C++: https://github.com/simple2d/simple2d
I go to run this command:
simple2d build c-code-test.cpp
I receive this response:
cc1plus: warning: command line option ‘-std=c11’ is valid for C/ObjC but not for C++
/usr/bin/ld: /tmp/ccl07DBG.o: undefined reference to symbol '_ZNSt8ios_base4InitD1Ev##GLIBCXX_3.4'
//usr/lib/x86_64-linux-gnu/libstdc++.so.6: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
Due to how fresh I am with Linux and C++ I am unable to make the correct inferences to solve this based on previous questions on stack overflow. I have installed libstdc++6 so I would have though it would be linked correctly.
Can someone walk me through in steps 1, 2, 3 ... Please? Thank you kindly!
The errors you see look to be from trying to compile C++ as C. The command line option is selecting the C11 standard, which is for C, not C++. The missing symbol is because the C++ library isn't being linked in, which also happens when linking a program as C.
I haven't used simple2d, but my guess here is that the compile script they wrote does not support C++ or there is some option you need to use C++. If we look at docs:
The simple2d build command is a helpful shortcut for compiling a
single source file. Of course, you can also use a compiler directly,
for example on Unix-like systems:
cc triangle.c `simple2d --libs` -o triangle
Why don't you try something like their example that invokes the compiler directly. But you would need to use g++ instead of cc. Something like: g++ c-code-test.cpp `simple2d --libs` -o c-code-test
This is a bug with the simple2d script.
They're basically using the wrong build command for C++.
You could work around it by patching in the fix I've linked to, or using the manual build step shown by TrentP.
Or wait for the next version after v1.1.0.
I was using flex and bison to build a simple calculator project I cloned from Github.
But after I typed make in terminal, I got the following message:
gcc -o calc calc.tab.c lex.yy.c -lfl
calc.y:48:1: warning: type specifier missing, defaults to 'int' [-Wimplicit-int]
main() {
^~~~
1 warning generated.
ld: library not found for -lfl
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [calc] Error 1
How could I resolve this problem?
let me guess, trying to use flex on OS/X?
Try -ll instead of -lfl
Using Flex on OS/X
So yea, the flex library name on OS/X is just arbitrarily different for some reason. OS/X is not exactly Linux, but it's pretty close. You have some options here.
You can just simply have a separate build system and source files for OS/X. Certainly Apple might like that with their pushing XCode, objective-C and not much interoperability.
You can build vs Linux and then engage with Mac Ports and Homebrew.
You can create your project using autotools. That's not an awesome link, learning this system is rough going, but it's a standard thing for Linux for sure. This will actually work, I find if you have the patience for it, OS/X is close enough that autotools based builds will work on it.
Lately, I've been turned on to Cocoapods, which I believe to be an attempt to join the open source community and XCode. It's kind of half 1 and 3 sorta with an emphasis on modularizing the external source and getting it compiled into a .app (via Xcode).
warning: type specifier missing, defaults to 'int'
mean that you should declare return type for main function. Place int in function difinition.
ld: library not found for -lfl
flag -l mean that compiller must use libfl.a to build programm. As #waTeim said above, for Mac OS you can use libl.a instead, but this lib can be not exist alse. There is another way is to place
%option noyywrap
at the top of flex *.l file. In this case you can compile without additional libs.
First some background - I have three VS2010 C++/OpenCL projects that compile and run fine on Windows 7 64-bit. I've been trying to compile and run each of them on Linux 64-bit (Ubuntu/Debian). The first two are compiling and running on linux and don't really use any external libraries. The third uses only Boost 1.50.0 and isn't compiling using the same method as the first two. So first let me go through what I did to get the first two to work.
I extracted only the source from the myriad of folders.
I ported windows specific code to linux specific code.
I wrote a bash script to generate the g++ command with all sources to compile them.
I ran the compile script to generate an output target file.
The bash script is as follows.
#!/bin/bash
SOURCE=""
for i in `ls *.h *.cpp *.hpp`; do
SOURCE+="${i} "
done
COMMAND="g++ -I/home/junkie/downloads/boost_1_51_0 -o out ${SOURCE} -L/opt/AMDAPP/lib/x86_64/ -I/opt/AMDAPP/include -lOpenCL -fpermissive"
echo -e "\n"
echo -e "${COMMAND}"
echo -e "\n"
$COMMAND
exit $?
And it generates and runs a command similar to following.
g++ -I/home/junkie/downloads/boost_1_51_0 -o out blah.cpp blah.h foo.hpp baz.cpp etc.cpp -L/opt/AMDAPP/lib/x86_64/ -I/opt/AMDAPP/include -lOpenCL -fpermissive
I compile using the following command.
./compile.sh &> log; echo $?; grep -ci error log; wc -l log
Now you may be wondering why I've adopted such unconventional and redundant means of getting a C++ project to compile and run on linux. Well because I'm new to the linux c and c++ toolchain and this was the quickest and simplest route I could figure out to get the job done and it did get the first two projects up and running. However, the third uses boost and this method isn't working and I need your help in figuring out what all these strange errors are.
The errors I'm getting are not actually from the project code but instead from Boost and AMD's opencl libraries code which is strange because the other projects were using opencl too and those worked fine.
Some examples of boost errors are below.
foo.hpp:2331:1: error: unterminated argument list invoking macro "BOOST_PP_CAT_I"
In file included from main.cpp:4:
foo2.hpp:1610:1: error: unterminated argument list invoking macro "BOOST_PP_CAT_I"
/home/junkie/downloads/boost_1_51_0/boost/preprocessor/cat.hpp:22: error: variable or field ‘BOOST_PP_CAT_I’ declared void /home/junkie/downloads/boost_1_51_0/boost/preprocessor/cat.hpp: At global scope:
/home/junkie/downloads/boost_1_51_0/boost/preprocessor/cat.hpp:22: error: variable or field ‘BOOST_PP_CAT_I’ declared void
/home/junkie/downloads/boost_1_51_0/boost/preprocessor/cat.hpp:22: error: expected ‘;’ at end of input
/home/junkie/downloads/boost_1_51_0/boost/preprocessor/cat.hpp:22: error: expected ‘;’ at end of input
/home/junkie/downloads/boost_1_51_0/boost/preprocessor/cat.hpp:22: error: expected ‘}’ at end of input
/home/junkie/downloads/boost_1_51_0/boost/preprocessor/cat.hpp:22: error: expected unqualified-id at end of input
/home/junkie/downloads/boost_1_51_0/boost/preprocessor/cat.hpp:22: error: expected ‘}’ at end of input
/home/junkie/downloads/boost_1_51_0/boost/preprocessor/cat.hpp:22: error: expected ‘}’ at end of input
foo.hpp:2331:1: error: unterminated argument list invoking macro "BOOST_PP_CAT_I"
Some examples of opencl errors are below.
In file included from /opt/AMDAPP/include/CL/cl_platform.h:35,
from /opt/AMDAPP/include/CL/cl.h:30,
from bar.h:7,
from fooGPU.hpp:6,
from main.cpp:4:
/usr/include/stdint.h:49: error: expected ‘;’ before ‘typedef’
In file included from /opt/AMDAPP/include/CL/cl.h:30,
from bar.h:7,
from fooGPU.hpp:6,
from main.cpp:4:
/opt/AMDAPP/include/CL/cl_platform.h:41: error: expected unqualified-id before string constant
main.cpp:136: error: expected ‘}’ at end of input
main.cpp:136: error: expected unqualified-id at end of input
main.cpp:136: error: expected ‘}’ at end of input
main.cpp:136: error: expected ‘}’ at end of input
The boost includes I'm Using are as follows.
#include <boost/preprocessor/punctuation/paren.hpp>
#include <boost/preprocessor/punctuation/comma.hpp>
#include <boost/static_assert.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/type_traits/is_base_of.hpp>
#include <boost/mpl/not.hpp>
#include <boost/mpl/int.hpp>
#include <boost/mpl/logical.hpp>
#include <boost/mpl/eval_if.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/array.hpp>
So, finally, my questions are as follows.
1) What is the root cause of these errors in light of the building method I'm using and how do I resolve this problem? Does order of files or library inclusion matter? I'm using a local source download of boost as part of my g++ command as instructed by boost documentation rather than prebuilt binaries as I'm not using anything that requires prebuilt binaries.
2) I realise that my way of building things is pretty primitive. I'm learning make and I've seen some recommendations to use cmake and kdevelop which I need to look into. The primary problem with using make is that these projects weren't written with make in mind so I'm not aware of the dependency graph between source files to create the makefile (if I'm thinking correctly; I'm still fairly new to it). If you have any recommendations of how to do things better please do enlighten me.
Thanks.
I finally managed to overcome this problem and here I provide a brief account of how. To be clear I don't know what the root cause of the original problem was. In other words - I don't know why the problem occurred. All I'm saying is that my workaround allowed me to resolve the issue and move onto other problems (compile time errors).
Essentially, to reiterate, the problem was that for whatever reason a project using boost wasn't compiling on Linux because all instances of the use of the BOOST_PP_CAT() function produced the following error.
error: unterminated argument list invoking macro "BOOST_PP_CAT_I"
For whatever reason the compiler wasn't able to correctly process the use of this function but was able to process the use of other boost functions such as BOOST_PP_LPAREN(), BOOST_PP_RPAREN() and BOOST_PP_COMMA. The problem looked almost certainly related to the preprocessing stage where the combined use of the aforementioned boost functions was resulting in an unterminated argument list.
To elaborate on the nature of the relevant code (which was not written by me thankfully) the prior developers had essentially used boost preprocessor functions to create a DSL that they could then re-use multiple times to generate a list of functions. It would have seemed a lot easier to me to simply write the functions directly but anyway that's another concern.
My work around was to change the relevant section of code so that it didn't use any BOOST_PP_CAT() functions but ultimately defined the exact same functions as before. I did this by substituting the use of BOOST_PP_CAT() with the code that was being generated by it. This overcame all instances of the error quoted above but left me with hundreds of other compile time errors in my efforts to migrate this project from windows to linux.
Although this was a very specific and unusual question with an equally specific and unusual answer I wanted to feed this back to dispel the mystery behind this problem. As to why this particular function was failing to preprocess/compile on linux but passing on Windows I don't know but would very much like to know. I can only assume it is a fundamental difference in the way VC++ performs preprocessing as opposed to g++ and clang or more specifically perhaps a difference in the order of resolution of nested functions in preprocessor directives. Who knows. Anyway, thanks for your help guys.
The unterminated argument list invoking macro error suggests a lacking closing parenthesis. Use your editor's parenthesis matcher to check it. Be sure that your source files are in Unix format, not in DOS format (e.g. with \n à la Unix, not with\r\n à la MSDOS, at each end-of-line). Use dos2unix if needed.
Otherwise, don't forget that you can run g++ -Wall -C -E -H -I/home/junkie/downloads/boost_1_51_0 yoursourcecode.cc to get the preprocessed form of yoursourcecode.cc, and, by redirecting that command, you can inspect that preprocessed form with the editor of your choice (like emacs).
As I commented, learn to use Gnu make (and if in trouble debugging your Makefile, which you should edit with a good editor like emacs, use remake -x to debug it).
And the -I/home/junkie/downloads/boost_1_51_0 looks very suspicious: even if Boost is often a header only library, it has, as far as I remember, an installation procedure on Unix (and Linux distributions often package Boost libs). You should install your Boost libraries as documented (and after having configured them), and likewise for OpenCL.
Hey friends
I am stuck at a serious linking error, I am getting an error like this referenced in section .rodata' of xxx defined in discarded section .text._xxx.
This is how I am compiling my program
g++ main.o CPQENReportBB1.o CPQENReportBB2.o CPQ10minRecord.o PQ10minconfiguration.o ENReportConfig.o CPQFreeRecording.o CPQFreeHistogramReport.o
I have 8 files, it is compiling correctly but while linking I get the previously mentioned error. (i am using g++ version 3.4.3)
In two files I am getting this error message; I tried to shuffle the files in linking but then it is giving error in another two files.
Please give any suggestion to solve this. I am using c++ templates
2 possible reasons:
the file format and the machine architecture.
the use of __attribute__((section))
I have been trying to build the logstalgia project (http://code.google.com/p/logstalgia/) on my Mac (10.5). Rather than having to link it to the system libraries correctly, I have built and added all of the dependencies to the project. I am new at this, but I do think I have done this correctly, mostly because I have had two of my friends who are much more experienced say so.
Adding the frameworks removed all of the compile errors, but I still get a linker error. It seems to not be able to find the main() function. I have verified I included main.cpp in the sources to be compiled (using XCode) and that there are no accidental double declarations. I have also verified that the main function is correctly declared (no missing brackets, etc).
It is as though XCode does not link in the correct order. Any help would be really appreciated, I am really excited to be down to a single error! (Hope fixing this does not open a floodgate).
Thanks,
Hamilton
PS - I can definitely provide a zip of the Xcode project if anyone is willing to look!
Checking Dependencies
Ld "/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Debug/Untitled" normal i386
cd "/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled"
setenv MACOSX_DEPLOYMENT_TARGET 10.5
/developer/usr/bin/g++-4.0 -arch i386 -isysroot /developer/SDKs/MacOSX10.5.sdk "-L/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Debug" -L/sw/lib "-L/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/../../pcre-7.9/.libs" -L/opt/local/lib -L/sw/lib "-F/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Debug" -F/Users/hamiltont/Downloads/logstalgia-0.9.2 -F2/src/SDL.framework "-F/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled" -filelist "/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Untitled.build/Debug/Untitled.build/Objects-normal/i386/Untitled.LinkFileList" -mmacosx-version-min=10.5 -framework OpenGL -lpcre -lSDL -lSDL_image-1.2.0 -prebind -o "/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Debug/Untitled"
Undefined symbols:
"_main", referenced from:
start in crt1.10.5.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
I got this error to go away. If I understand, essentially SDL re-names the main function, so that it can do some stuff, then run your application, then clean up. Turns out that if you are building in Xcode, you must use ObjectiveC to compile your application.
In Xcode, telling the linker to try and use SDL_main(), rather than just main() does not work (for some technical reasons that are a bit beyond me). So, you include a few Objective C files. In Oc, you get the benefit of being able to say explicitely what the name of your main class is. Hence, the Objective C files you include seem to do nothing more than let Xcode know to look for SDL_main().
In summary, this really had nothing to do with Logstalgia, but was entirely a problem with getting SDL to link correctly in Xcode. This link is talking about this problem exactly. The SDLMain.h and SDLMain.m are Objective C files. If you can't find them, try googleing "Setting up SDL templates in Xcode." I installed the templates in Xcode, used one of them to create an empty project that would compile, link, and run (and promptly do nothing!) and then I added the project files I wanted to the pre-configured project.
Thanks!
Double-check the link file list to make sure main.cpp's object file is present there:
/Users/hamiltont/Downloads/logstalgia-0.9.2 2/Untitled/build/Untitled.build/Debug/Untitled.build/Objects-normal/i386/Untitled.LinkFileList
You might also want to preprocess the main.cpp to make sure main isn't getting inadvertently renamed (via a rogue macro) or omitted (via a rogue #if).