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.
diff --git a/Doc/api/concrete.tex b/Doc/api/concrete.tex
index 9762924..26a82d3 100644
--- a/Doc/api/concrete.tex
+++ b/Doc/api/concrete.tex
@@ -586,7 +586,16 @@
\begin{cfuncdesc}{int}{_PyString_Resize}{PyObject **string, int newsize}
A way to resize a string object even though it is ``immutable''.
Only use this to build up a brand new string object; don't use this
- if the string may already be known in other parts of the code.
+ if the string may already be known in other parts of the code. It
+ is an error to call this function if the refcount on the input string
+ object is not one.
+ Pass the address of an existing string object as an lvalue (it may
+ be written into), and the new size desired. On success, \var{*string}
+ holds the resized string object and 0 is returned; the address in
+ \var{*string} may differ from its input value. If the
+ reallocation fails, the original string object at \var{*string} is
+ deallocated, \var{*string} is set to \NULL{}, a memory exception is set,
+ and -1 is returned.
\end{cfuncdesc}
\begin{cfuncdesc}{PyObject*}{PyString_Format}{PyObject *format,
diff --git a/Modules/_ssl.c b/Modules/_ssl.c
index f5ab2b6..1b05e40 100644
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -331,8 +331,8 @@
Py_DECREF(buf);
return PySSL_SetError(self, count);
}
- if (count != len && _PyString_Resize(&buf, count) < 0)
- return NULL;
+ if (count != len)
+ _PyString_Resize(&buf, count);
return buf;
}
diff --git a/Modules/cPickle.c b/Modules/cPickle.c
index 2ffba48..a6c5e9d 100644
--- a/Modules/cPickle.c
+++ b/Modules/cPickle.c
@@ -1252,14 +1252,8 @@
*p++ = (char) ch;
}
*p = '\0';
- if (_PyString_Resize(&repr, p - q))
- goto onError;
-
+ _PyString_Resize(&repr, p - q);
return repr;
-
- onError:
- Py_DECREF(repr);
- return NULL;
}
diff --git a/Modules/cdmodule.c b/Modules/cdmodule.c
index b977277..25add3e 100644
--- a/Modules/cdmodule.c
+++ b/Modules/cdmodule.c
@@ -251,8 +251,7 @@
return NULL;
}
if (n < numframes)
- if (_PyString_Resize(&result, n * sizeof(CDFRAME)))
- return NULL;
+ _PyString_Resize(&result, n * sizeof(CDFRAME));
return result;
}
diff --git a/Modules/clmodule.c b/Modules/clmodule.c
index ef3d77a..70e8f8e 100644
--- a/Modules/clmodule.c
+++ b/Modules/clmodule.c
@@ -135,8 +135,7 @@
}
if (compressedBufferSize < frameBufferSize)
- if (_PyString_Resize(&compressedBuffer, compressedBufferSize))
- return NULL;
+ _PyString_Resize(&compressedBuffer, compressedBufferSize);
return compressedBuffer;
}
diff --git a/Modules/linuxaudiodev.c b/Modules/linuxaudiodev.c
index fa2e441..7d4abc9 100644
--- a/Modules/linuxaudiodev.c
+++ b/Modules/linuxaudiodev.c
@@ -158,8 +158,7 @@
return NULL;
}
self->x_icount += count;
- if (_PyString_Resize(&rv, count) == -1)
- return NULL;
+ _PyString_Resize(&rv, count);
return rv;
}
diff --git a/Modules/regexmodule.c b/Modules/regexmodule.c
index d449604..4c7035e 100644
--- a/Modules/regexmodule.c
+++ b/Modules/regexmodule.c
@@ -516,11 +516,8 @@
return NULL;
}
/* _PyString_Resize() decrements npattern on failure */
- if (_PyString_Resize(&npattern, n - v) == 0)
- return npattern;
- else {
- return NULL;
- }
+ _PyString_Resize(&npattern, n - v);
+ return npattern;
}
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index 53952fc..21fcab0 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -1402,8 +1402,8 @@
Py_DECREF(buf);
return s->errorhandler();
}
- if (n != len && _PyString_Resize(&buf, n) < 0)
- return NULL;
+ if (n != len)
+ _PyString_Resize(&buf, n);
return buf;
}
diff --git a/Modules/stropmodule.c b/Modules/stropmodule.c
index 0d5b75c..9a68b20 100644
--- a/Modules/stropmodule.c
+++ b/Modules/stropmodule.c
@@ -215,10 +215,8 @@
}
slen = PyString_GET_SIZE(item);
while (reslen + slen + seplen >= sz) {
- if (_PyString_Resize(&res, sz * 2)) {
- Py_DECREF(res);
+ if (_PyString_Resize(&res, sz * 2) < 0)
return NULL;
- }
sz *= 2;
p = PyString_AsString(res) + reslen;
}
@@ -231,10 +229,7 @@
p += slen;
reslen += slen;
}
- if (_PyString_Resize(&res, reslen)) {
- Py_DECREF(res);
- res = NULL;
- }
+ _PyString_Resize(&res, reslen);
return res;
}
@@ -257,8 +252,7 @@
}
slen = PyString_GET_SIZE(item);
while (reslen + slen + seplen >= sz) {
- if (_PyString_Resize(&res, sz * 2)) {
- Py_DECREF(res);
+ if (_PyString_Resize(&res, sz * 2) < 0) {
Py_DECREF(item);
return NULL;
}
@@ -275,10 +269,7 @@
reslen += slen;
Py_DECREF(item);
}
- if (_PyString_Resize(&res, reslen)) {
- Py_DECREF(res);
- res = NULL;
- }
+ _PyString_Resize(&res, reslen);
return res;
}
@@ -989,8 +980,8 @@
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;
}
diff --git a/Modules/zlibmodule.c b/Modules/zlibmodule.c
index a3891f7..cfb71ae 100644
--- a/Modules/zlibmodule.c
+++ b/Modules/zlibmodule.c
@@ -255,9 +255,8 @@
/* fall through */
case(Z_OK):
/* need more memory */
- if (_PyString_Resize(&result_str, r_strlen << 1) == -1) {
+ if (_PyString_Resize(&result_str, r_strlen << 1) < 0) {
inflateEnd(&zst);
- result_str = NULL;
goto error;
}
zst.next_out = (unsigned char *)PyString_AS_STRING(result_str) \
@@ -414,10 +413,8 @@
/* while Z_OK and the output buffer is full, there might be more output,
so extend the output buffer and try again */
while (err == Z_OK && self->zst.avail_out == 0) {
- if (_PyString_Resize(&RetVal, length << 1) == -1) {
- RetVal = NULL;
+ if (_PyString_Resize(&RetVal, length << 1) < 0)
goto error;
- }
self->zst.next_out = (unsigned char *)PyString_AS_STRING(RetVal) \
+ length;
self->zst.avail_out = length;
@@ -438,9 +435,7 @@
RetVal = NULL;
goto error;
}
- if (_PyString_Resize(&RetVal,
- self->zst.total_out - start_total_out) < 0)
- RetVal = NULL;
+ _PyString_Resize(&RetVal, self->zst.total_out - start_total_out);
error:
LEAVE_ZLIB
@@ -510,10 +505,8 @@
if (max_length && length > max_length)
length = max_length;
- if (_PyString_Resize(&RetVal, length) == -1) {
- RetVal = NULL;
+ if (_PyString_Resize(&RetVal, length) < 0)
goto error;
- }
self->zst.next_out = (unsigned char *)PyString_AS_STRING(RetVal) \
+ old_length;
self->zst.avail_out = length - old_length;
@@ -561,8 +554,7 @@
goto error;
}
- if (_PyString_Resize(&RetVal, self->zst.total_out - start_total_out) < 0)
- RetVal = NULL;
+ _PyString_Resize(&RetVal, self->zst.total_out - start_total_out);
error:
LEAVE_ZLIB
@@ -612,10 +604,8 @@
/* while Z_OK and the output buffer is full, there might be more output,
so extend the output buffer and try again */
while (err == Z_OK && self->zst.avail_out == 0) {
- if (_PyString_Resize(&RetVal, length << 1) == -1) {
- RetVal = NULL;
+ if (_PyString_Resize(&RetVal, length << 1) < 0)
goto error;
- }
self->zst.next_out = (unsigned char *)PyString_AS_STRING(RetVal) \
+ length;
self->zst.avail_out = length;
@@ -651,8 +641,7 @@
goto error;
}
- if (_PyString_Resize(&RetVal, self->zst.total_out - start_total_out) < 0)
- RetVal = NULL;
+ _PyString_Resize(&RetVal, self->zst.total_out - start_total_out);
error:
LEAVE_ZLIB
diff --git a/Objects/fileobject.c b/Objects/fileobject.c
index 3dd1034..029a270 100644
--- a/Objects/fileobject.c
+++ b/Objects/fileobject.c
@@ -1317,9 +1317,7 @@
goto error;
}
cleanup:
- if (big_buffer) {
- Py_DECREF(big_buffer);
- }
+ Py_XDECREF(big_buffer);
return list;
}
diff --git a/Objects/stringobject.c b/Objects/stringobject.c
index d3c9e4b..5bad04e 100644
--- a/Objects/stringobject.c
+++ b/Objects/stringobject.c
@@ -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)
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index c4c8d8d..9a3e456 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -927,10 +927,7 @@
*out++ = '-';
}
- if (_PyString_Resize(&v, out - start)) {
- Py_DECREF(v);
- return NULL;
- }
+ _PyString_Resize(&v, out - start);
return v;
}
@@ -1764,7 +1761,7 @@
/* Resize the string if necessary */
if (offset + 12 > PyString_GET_SIZE(repr)) {
if (_PyString_Resize(&repr, PyString_GET_SIZE(repr) + 100))
- goto onError;
+ return NULL;
p = PyString_AS_STRING(repr) + offset;
}
@@ -1847,14 +1844,8 @@
*p++ = PyString_AS_STRING(repr)[1];
*p = '\0';
- if (_PyString_Resize(&repr, p - PyString_AS_STRING(repr)))
- goto onError;
-
+ _PyString_Resize(&repr, p - PyString_AS_STRING(repr));
return repr;
-
- onError:
- Py_DECREF(repr);
- return NULL;
}
PyObject *PyUnicode_EncodeUnicodeEscape(const Py_UNICODE *s,
@@ -1985,14 +1976,8 @@
*p++ = (char) ch;
}
*p = '\0';
- if (_PyString_Resize(&repr, p - q))
- goto onError;
-
+ _PyString_Resize(&repr, p - q);
return repr;
-
- onError:
- Py_DECREF(repr);
- return NULL;
}
PyObject *PyUnicode_AsRawUnicodeEscapeString(PyObject *unicode)
@@ -2092,8 +2077,7 @@
}
/* Resize if error handling skipped some characters */
if (s - start < PyString_GET_SIZE(repr))
- if (_PyString_Resize(&repr, s - start))
- goto onError;
+ _PyString_Resize(&repr, s - start);
return repr;
onError:
@@ -2240,8 +2224,7 @@
}
/* Resize if error handling skipped some characters */
if (s - start < PyString_GET_SIZE(repr))
- if (_PyString_Resize(&repr, s - start))
- goto onError;
+ _PyString_Resize(&repr, s - start);
return repr;
onError:
@@ -2588,12 +2571,11 @@
Py_DECREF(x);
}
if (s - PyString_AS_STRING(v) < PyString_GET_SIZE(v))
- if (_PyString_Resize(&v, (int)(s - PyString_AS_STRING(v))))
- goto onError;
+ _PyString_Resize(&v, (int)(s - PyString_AS_STRING(v)));
return v;
onError:
- Py_DECREF(v);
+ Py_XDECREF(v);
return NULL;
}
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 06d8616..aa65ebc 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -1993,8 +1993,8 @@
Py_DECREF(item);
}
- if (j < len && _PyString_Resize(&result, j) < 0)
- return NULL;
+ if (j < len)
+ _PyString_Resize(&result, j);
return result;