lundi 29 septembre 2014

Python/C API gcc compile warning unused variable


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I have been trying to embed python into c. I am on Linux Mint 17 and installed python-dev. I have been following the documentation on http://ift.tt/SR7VzM I was able to compile the first example using the following.



#include <Python.h>

int
main(int argc, char *argv[])
{
Py_SetProgramName(argv[0]); /* optional but recommended */
Py_Initialize();
PyRun_SimpleString("from time import time,ctime\n"
"print 'Today is',ctime(time())\n");
Py_Finalize();
return 0;
}


I compiled using gcc with this command: gcc python2.7-config --cflags test.c -o test python2.7-config --ldflags


The program compiles fine and works. When I tried to compile the pure embedding example here:



#include <Python.h>

int main(int argc, char *argv[])
{
PyObject *pName, *pModule, *pDict, *pFunc;
PyObject *pArgs, *pValue;
int i;

if (argc < 3) {
fprintf(stderr,"Usage: call pythonfile funcname [args]\n");
return 1;
}

Py_Initialize();
pName = PyString_FromString(argv[1]);
/* Error checking of pName left out */

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

if (pModule != NULL) {
pFunc = PyObject_GetAttrString(pModule, argv[2]);
/* pFunc is a new reference */

if (pFunc && PyCallable_Check(pFunc)) {
pArgs = PyTuple_New(argc - 3);
for (i = 0; i < argc - 3; ++i) {
pValue = PyInt_FromLong(atoi(argv[i + 3]));
if (!pValue) {
Py_DECREF(pArgs);
Py_DECREF(pModule);
fprintf(stderr, "Cannot convert argument\n");
return 1;
}
/* pValue reference stolen here: */
PyTuple_SetItem(pArgs, i, pValue);
}
pValue = PyObject_CallObject(pFunc, pArgs);
Py_DECREF(pArgs);
if (pValue != NULL) {
printf("Result of call: %ld\n", PyInt_AsLong(pValue));
Py_DECREF(pValue);
}
else {
Py_DECREF(pFunc);
Py_DECREF(pModule);
PyErr_Print();
fprintf(stderr,"Call failed\n");
return 1;
}
}
else {
if (PyErr_Occurred())
PyErr_Print();
fprintf(stderr, "Cannot find function \"%s\"\n", argv[2]);
}
Py_XDECREF(pFunc);
Py_DECREF(pModule);
}
else {
PyErr_Print();
fprintf(stderr, "Failed to load \"%s\"\n", argv[1]);
return 1;
}
Py_Finalize();
return 0;
}


I used the same gcc compile command and I got the following error:



test.c: In function ‘main’:
test.c:6:33: warning: unused variable ‘pDict’ [-Wunused-variable]
PyObject *pName, *pModule, *pDict, *pFunc;


Why does this happen and how do I solve this?



asked 1 min ago







Python/C API gcc compile warning unused variable

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