foolib.c

typedef struct post {
    char *x;
    char *y;
    int x_z;
} post_t;


void
foo (post_t *o, char *src)
{
    int i=0;

    char *p = src;
    int len = strlen(src);

    for (; *p != '\0'; i++, p++) {
        if (*p == 'x') {
            o->x = p;
            o->x_z = len-i;
        }
    }
    o->y=src;
}

test.py

from ctypes import *

foolib = CDLL("./foolib.so")

class Post(Structure):
    _fields_ = (
        ("x", c_void_p),
        ("y", c_void_p),
        ("x_z", c_int),
    )

o = Post()

s = "iooxooiddfggggggggggggvd"

foolib.foo(byref(o), create_string_buffer(s))

print o.x_z

print string_at(o.x, o.x_z)
print string_at(o.y, len(s))

打印结果为何是

foo ➤ python test.py                                                                                                                   
21
ooiddfggggggggggggvd
ooiddfggggggggggggvd

不应该 输出下面的吗 :

21
iooxooiddfggggggggggggvd
ooiddfggggggggggggvd