CODEWITHSUNDEEP
pythoncmemory-leakscython
Asiful Nobel
Asiful Nobel

Reputation: 343

Cython function memory leak

I have converted a python function to a cython one. Now the function works as it is supposed to. But I am getting a lot of memory leak when the main program calls this function multiple times. I have freed the memory that I allocated dynamically, but it does not seem to work.

What am I doing wrong here?

from cpython.mem cimport PyMem_Malloc, PyMem_Free

def longest_common_substring(refWord, stemWord):
cdef:
    int longest, x_longest
    int x, y, k
    Py_ssize_t lengthRefWord
    Py_ssize_t lengthStemWord
    wchar_t *referenceWord = PyUnicode_AsWideCharString(refWord, &lengthRefWord)
    wchar_t *stemmableWord = PyUnicode_AsWideCharString(stemWord, &lengthStemWord)
    int t1 = lengthRefWord+1
    int t2 = lengthStemWord+1
    int **m = <int **> PyMem_Malloc(t1 * sizeof(int *))
    wchar_t tempChar1;
    wchar_t tempChar2;
longest = 0
x_longest = 0

for k in range(t1):
   m[k] = <int *> PyMem_Malloc(t2 * sizeof(int))
for x in range(0, t1):
    for y in range(0, t2):
        m[x][y] = 0

for x in range(1, t1):
    for y in range(1, t2):
       tempChar1 = referenceWord[x - 1]
       tempChar2 = stemmableWord[y - 1]

       if tempChar1 == tempChar2:
           m[x][y] = m[x - 1][y - 1] + 1
           if m[x][y] > longest:
               longest = m[x][y]
               x_longest = x
       else:
           m[x][y] = 0
for k in range(t1):
   PyMem_Free(m[k])
PyMem_Free(m)
return refWord[x_longest - longest: x_longest]

Upvotes: 2

Views: 893

Answers (1)

DavidW
DavidW

Reputation: 30891

PyUnicode_AsWideCharString allocates memory that you have to free. The documentation says

Returns a buffer allocated by PyMem_Alloc() (use PyMem_Free() to free it) on success.

You get two strings from this function but free neither of them.

Upvotes: 3

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