Mercurial > cpython-lru_cache-weakref
diff Objects/stringobject.c @ 23295:6fa76b4e59fe legacy-trunk
Repair widespread misuse of _PyString_Resize. Since it's clear people
don't understand how this function works, also beefed up the docs. The
most common usage error is of this form (often spread out across gotos):
if (_PyString_Resize(&s, n) < 0) {
Py_DECREF(s);
s = NULL;
goto outtahere;
}
The error is that if _PyString_Resize runs out of memory, it automatically
decrefs the input string object s (which also deallocates it, since its
refcount must be 1 upon entry), and sets s to NULL. So if the "if"
branch ever triggers, it's an error to call Py_DECREF(s): s is already
NULL! A correct way to write the above is the simpler (and intended)
if (_PyString_Resize(&s, n) < 0)
goto outtahere;
Bugfix candidate.
| author | Tim Peters <tim.peters@gmail.com> |
|---|---|
| date | Sat, 27 Apr 2002 18:44:32 +0000 |
| parents | e639e34ef901 |
| children | 1be6e79b1d46 |
line wrap: on
line diff
--- a/Objects/stringobject.c Sat Apr 27 18:03:26 2002 +0000 +++ b/Objects/stringobject.c Sat Apr 27 18:44:32 2002 +0000 @@ -1869,8 +1869,8 @@ return input_obj; } /* Fix the size of the resulting string */ - if (inlen > 0 &&_PyString_Resize(&result, output-output_start)) - return NULL; + if (inlen > 0) + _PyString_Resize(&result, output - output_start); return result; } @@ -2927,7 +2927,14 @@ is only one module referencing the object. You can also think of it as creating a new string object and destroying the old one, only more efficiently. In any case, don't use this if the string may - already be known to some other part of the code... */ + already be known to some other part of the code... + Note that if there's not enough memory to resize the string, the original + string object at *pv is deallocated, *pv is set to NULL, an "out of + memory" exception is set, and -1 is returned. Else (on success) 0 is + returned, and the value in *pv may or may not be the same as on input. + As always, an extra byte is allocated for a trailing \0 byte (newsize + does *not* include that), and a trailing \0 byte is stored. +*/ int _PyString_Resize(PyObject **pv, int newsize)