Problem in printing array of char pointer passing from Python

Question

My following C code works quite well, till my Python code trying to pass an array of char pointer to it.

The output I obtain is

The file_name is python-file

Another 3 string is not being printed out. Anything I had missed out?

C Code

#include <iostream>
#include "c_interface.h"

int foo(const char* file_name, const char** names) {
    std::cout << "The file_name is " << file_name << std::endl;
    while (*names) {
        std::cout << "The name is " << *names << std::endl;
        names++;
    }
    return 0;
}

/*
int main() {
    const char *c[] = {"123gh", "456443432", "789", 0};
    foo("hello", c);
    getchar();
}
*/

Python Code

#!c:/Python27/python.exe -u

from ctypes import *

name0 = "NAME0"
name1 = "NAME1"
name2 = "NAME2"

names = ((c_char_p * 1024) * 4)()
names[0].value = name0
names[1].value = name1
names[2].value = name2
names[3].value = 0

libc = CDLL("foo.dll")
libc.foo("python-file", names)

Jim Brissom · Accepted Answer · 2011-01-14 03:10:01Z

1

Using and compiling your C++ code, I can only repeat the code I already stated in my last answer:

In [1]: import ctypes

In [2]: lib = ctypes.CDLL("libfoo.so.1.0")

In [3]: names = (ctypes.c_char_p*4)()

In [4]: names[0] = "NAME0"

In [5]: names[1] = "NAME1"

In [6]: names[2] = "NAME2"

In [7]: names[3] = 0

In [8]: lib.foo("whatever", names)
The file_name is whatever
The name is NAME0
The name is NAME1
The name is NAME2
Out[8]: 0

As a suggestion for you, open up your Python/IPython shell, execute your line

names = ((c_char_p * 1024) * 4)()

...and check the first element names[0] directory entry, using dir. Or, try to access the value attribute for a start.

edited Jan 14, 2011 at 3:10

answered Jan 14, 2011 at 3:04

Jim Brissom

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