在C中嵌入Python:链接时出错 – 对PyString_AsString的未定义引用

我试图在C程序中嵌入一个python程序.我的操作系统是Ubuntu 14.04

我尝试在相同的C代码库(作为单独的应用程序)中嵌入python 2.7和python 3.4解释器.编译和链接在嵌入python 2.7时有用,但不适用于python 3.4.它在链接器阶段失败.

这是我的C代码(只是一个例子不是真正的代码)

simple.c

#include <stdio.h>
#include <Python.h>

int main(int argc, char *argv[])
{
    PyObject *pName, *pModule, *pFunc, *pValue;
    char module[] = "get_version";
    char func[] = "get_version";
    char module_path[] = ".";

    Py_Initialize();
    PyObject *sys_path = PySys_GetObject("path");
    PyList_Append(sys_path, PyUnicode_FromString(module_path));

    pName = PyUnicode_FromString(module);
    pModule = PyImport_Import(pName);
    Py_DECREF(pName);

    if(pModule != NULL)
    {
        pFunc = PyObject_GetAttrString(pModule, func);
        if (pFunc && PyCallable_Check(pFunc))
        {
            pValue = PyObject_CallObject(pFunc, NULL);
            if (pValue != NULL) {
                printf("Python version: %s\n", PyString_AsString(pValue));
                Py_DECREF(pValue);
            }
            else {
                Py_DECREF(pFunc);
                Py_DECREF(pModule);
                PyErr_Print();
                fprintf(stderr,"Call failed\n");
                return 1;
            }
        }
    }

    Py_Finalize();
    return 0;
}

get_version.py

import sys

def get_version():
    version = '.'.join(str(v) for v in sys.version_info[:3])
    print("version: ", version)
    return version

我用gcc编译程序.首先将编译和链接标志设置为python 2.7我使用以下命令运行编译和链接:

gcc `python-config --cflags` simple.c `python-config --ldflags`

标志扩展为:

python-config –cflags:-I /usr/include / python2.7 -I /usr/include / x86_64-linux-gnu / python2.7 -fno-strict-aliasing -D_FORTIFY_SOURCE = 2 -g -fstack-protector – -param = ssp-buffer-size = 4 -Wformat -Werror = format-security -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes

python-config –ldflags:-L /usr/lib / python2.7 / config-x86_64-linux-gnu -L /usr/lib -lpthread -ldl -lutil -lm -lpython2.7 -Xlinker -export-dynamic – W1,-O1-Wl,-Bsymbolic-functions

它没有任何问题,工作正常.当我尝试用python3.4标志编译它时,它失败了:

gcc `python3-config --cflags` simple.c `python3-config --ldflags`

标志扩展为:

python-config –cflags:-I /usr/include / python3.4m -I /usr/include / python3.4m -Wno-unused-result -g -fstack-protector –param = ssp-buffer-size = 4 -Wformat -Werror = format-security -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes

python-config –ldflags:-L /usr/lib / python3.4 / config-3.4m-x86_64-linux-gnu -L /usr/lib -lpython3.4m -lpthread -ldl -lutil -lm -Xlinker -export -dynamic -Wl,-O1 -Wl,-Bsymbolic-functions

错误信息:

simple.c: In function ‘main’:
simple.c:27:17: warning: implicit declaration of function ‘PyString_AsString’ [-Wimplicit-function-declaration]
                 printf("Python version: %s\n", PyString_AsString(pValue));
                 ^
simple.c:27:17: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Wformat=]
/tmp/ccaoMdTo.o: In function `main':
/home/vagrant/c_python_api/simple.c:27: undefined reference to `PyString_AsString'
collect2: error: ld returned 1 exit status

我尝试通过更改指定链接器对象的顺序.但没有运气.知道为什么会这样吗?

谢谢您的帮助!!

最佳答案
Python 3 does not have PyString_AsString any more; Python 3 str对应Python 2 unicode对象;在Python 3中处理str的函数的名称是在C-API中以PyUnicode_为前缀的.

这样一行:

printf("Python version: %s\n", PyString_AsString(pValue));

可以更改为在Python 3上使用PyUnicode_AsUTF8

#if PY_MAJOR_VERSION >= 3
printf("Python version: %s\n", PyUnicode_AsUTF8(pValue));
#else
printf("Python version: %s\n", PyString_AsString(pValue));
#endif

(而不是将NULL传递给printf%s将具有未定义的行为,因此您需要检查是否返回了非NULL指针)

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