Set Xcode flags in order to embed python in my C++ project

Question

I'm trying to embed python in my C++ project. I need to do it in order to use some functions that implement the Kolmogorov-Smirnov Test that are not available in C++.

For now I'm just trying to see if Xcode is able to link and compile a simple program that embeds Python. The code I'm trying to compile is the following:

#include<Python/Python.h>

int main(int argc, const char * argv[]) {

    Py_Initialize();
    PyObject* variable;
    Py_Finalize();
    return 0;
}

As far as I can understand from the instructions I've read here: 1. Embedding Python in Another Application - 1.6 Compiling and Linking under Unix-like systems and here: Python/C API Reference Manual - Introduction in order for this to compile I have to add some additional flags to the compiler and the linker.

In order to find out which flags should I add, I've run the following two commands in my terminal (of which I include the corresponding output):

$ python3.6-config --cflags          
-I/Users/user/anaconda3/include/python3.6m -I/Users/user/anaconda3/include/python3.6m -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -I/Users/user/anaconda3/include -arch x86_64 -I/Users/user/anaconda3/include -arch x86_64

$ python3.6-config --ldflags
-lpython3.6m -ldl -framework CoreFoundation -Wl,-stack_size,1000000 -framework CoreFoundation

Where I replaced the actual name of my user folder with user.

Now, in order to add these flags to the Xcode compiler and linker I went to my project settings window and under Build Settings -> Other C Flags and Build Settings -> Other Linker Flags I added the flags that I've reported above.

But when I compile I get this error:

Apple Mach-O Linker (ld) Error Group
clang: error: linker command failed with exit code 1 (use -v to see invocation)

And it doesn't go away even if I comment all the lines in the main function except for return 0.

I don't understand what I'm doing wrong.

I'm using Xcode 8.3.2 and my Python distribution is: Python 3.6.1 |Anaconda 4.4.0

score 0 · Accepted Answer · answered Jun 02 '17 at 15:09

Ok, I think I've found a solution. Not sure if it's actually the right one (since I'm not an expert and I don't really understand the reason why now it works), but I'm going to post it anyway.

The thing is that if you look at the instructions in this page: 1. Embedding Python in Another Application - 1.6. Compiling and Linking under Unix-like systems you can see that when executing the command python3.6-config --ldflags the output contains a flag -L/opt/lib/python3.4/config-3.4m while in my case it doesn't.

So after figuring out that the flag that gave me the linking error was -lpython3.6m, I thought that maybe it was due to the fact that the linker couldn't find the directory in which my python distribution was or something like that.

So I looked in my hard drive for a path to a folder with a name similar to the one shown on the webpage and I found that /Users/user/anaconda3/lib/python3.6/config-3.6m-darwin was a path to a folder with a name very similar to the one I was looking for, except for the "-darwin" at the end of the folder's name that's probably there because I'm on a macOS distribution (maybe that's why the command python3.6-config --ldflags didn't find it? I don't know).

After this I just added -L/Users/user/anaconda3/lib/python3.6/config-3.6m-darwin at the beginning of Xcode's "Other Liker Flags" and everything (almost) compiled just fine.

I say "almost" because I also had to rename the include at the beginning of my code from #include<Python/Python.h> to #include<Python.h> (maybe because by using the first one I'm including the system default Python distribution while with the second I'm including the Anaconda one? Again, I don't know).

Anyway now everything compiles just fine and so I thought to share how I did it in case somebody else is in the same situation.

Set Xcode flags in order to embed python in my C++ project

1 Answers1