Reference undefined to functions in python-dev header

Question

I'm trying to embedding some Python code into C; It's the first time I do a thing like that.

Here is the simple code of my first attempt copied by a guide on internet:

#include <Python.h>
void exec_pycode(const char* code)
{
  Py_Initialize();
  PyRun_SimpleString(code);
  Py_Finalize();
}

int main(int argc, char **argv) {
    exec_pycode(argv[1]);
    return 0;
}

So I've installed python3.4-dev package.

Then for having info for the linker I typed:

pkg-config --cflags --libs python3

Then I tried to compile my code:

gcc -std=c99 -o main -I /usr/local/include/python3.4m  -L /usr/local/lib -lpython3.4m main.c

(according the command before)

but this is the result:

/tmp/ccJFmdcr.o: in function "exec_pycode":
main.c:(.text+0xd): reference undefined to "Py_Initialize"
main.c:(.text+0x1e): reference undefined to "PyRun_SimpleStringFlags"
main.c:(.text+0x23): reference undefined to "Py_Finalize"
collect2: error: ld returned 1 exit status

It would seem that there is a problem with linking phase, but I can't understend where is the problem seeing that i've passed to the linker the exact paths of the header and of the library. How can I solve that problem?

user12205 · Accepted Answer · 2015-05-04 22:09:44Z

2

Try reordering your compilation command, such that all linking options are specified after your C source files:

gcc -std=c99 -o main -I /usr/local/include/python3.4m main.c \
  -L /usr/local/lib -lpython3.4m

answered May 4, 2015 at 22:09

user12205

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3 Comments

Matteo Arella Over a year ago

yes I've resolved the previous problem but now I've that problem: /usr/local/lib/libpython3.4m.a(pytime.o): in function "_PyTime_ObjectToTime_t": /home/matteo/Scrivania/Python-3.4.3/Python/pytime.c:212: undefined reference to "ceil" /home/matteo/Scrivania/Python-3.4.3/Python/pytime.c:214: undefined reference to "floor" /usr/local/lib/libpython3.4m.a(pytime.o): in function "_PyTime_ObjectToDenominator": /home/matteo/Scrivania/Python-3.4.3/Python/pytime.c:173: undefined reference to "ceil" ...(and all other maths functions) So I tried to recompile adding -lm but I didn't resolve the problem :/

user12205 Over a year ago

@MatteoArella Where did you add -lm? Try a few different places - before -lpython3.4m and after, and see which one works. If neither works, try running python-config --ldflags in a terminal and use those as the linker flags.

user12205 Over a year ago

Note that you may have to change the order of flags in the python-config output - if it doesn't work try moving -lpython3.4m after all the -L flags and before all the -l flags.

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