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refactor signed (to) converters #12

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184 changes: 70 additions & 114 deletions Objects/longobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -514,18 +514,6 @@
return (PyObject *)v;
}

/* Checking for overflow in PyLong_AsLong is a PITA since C doesn't define
* anything about what happens when a signed integer operation overflows,
* and some compilers think they're doing you a favor by being "clever"
* then. The bit pattern for the largest positive signed long is
* (unsigned long)LONG_MAX, and for the smallest negative signed long
* it is abs(LONG_MIN), which we could write -(unsigned long)LONG_MIN.
* However, some other compilers warn about applying unary minus to an
* unsigned operand. Hence the weird "0-".
*/
#define PY_ABS_LONG_MIN (0-(unsigned long)LONG_MIN)
#define PY_ABS_SSIZE_T_MIN (0-(size_t)PY_SSIZE_T_MIN)

static inline unsigned long
unroll_digits_ulong(PyLongObject *v, Py_ssize_t *iptr)
{
Expand Down Expand Up @@ -574,6 +562,39 @@
return x;
}

/* Checking for overflow in PyLong_AsLong is a PITA since C doesn't define
* anything about what happens when a signed integer operation overflows,
* and some compilers think they're doing you a favor by being "clever"
* then. The bit pattern for the largest positive signed long is
* (unsigned long)LONG_MAX, and for the smallest negative signed long
* it is abs(LONG_MIN), which we could write -(unsigned long)LONG_MIN.
* However, some other compilers warn about applying unary minus to an
* unsigned operand. Hence the weird "0-".
*/

#define UNROLL_DIGITS(v, suff, type, utype, UMAX, TYPE) \
i = _PyLong_DigitCount(v); \
sign = _PyLong_NonCompactSign(v); \
\
utype x = unroll_digits_##suff(v, &i); \
while (--i >= 0) { \
if (x > (UMAX >> PyLong_SHIFT)) { \
goto fail; \
} \
x = (x << PyLong_SHIFT) | v->long_value.ob_digit[i]; \
} \
/* Haven't lost any bits, but casting to utype requires */ \
/* extra care (see comment above). */ \
if (x <= (utype)TYPE##_MAX) { \
res = (type)x * sign; \
} \
else if (sign < 0 && x == (0-(utype)TYPE##_MIN)) { \
res = TYPE##_MIN; \
} \
else { \
goto fail; \
}

/* Get a C long int from an int object or any object that has an __index__
method.

Expand All @@ -588,7 +609,7 @@
{
/* This version originally by Tim Peters */
PyLongObject *v;
long res;
long res = -1;
Py_ssize_t i;
int sign;
int do_decref = 0; /* if PyNumber_Index was called */
Expand All @@ -613,11 +634,9 @@
Py_ssize_t tmp = _PyLong_CompactValue(v);
if (tmp < LONG_MIN) {
*overflow = -1;
res = -1;
}
else if (tmp > LONG_MAX) {
*overflow = 1;
res = -1;
}
else {
res = (long)tmp;
Expand All @@ -627,31 +646,10 @@
#endif
}
else {
res = -1;
i = _PyLong_DigitCount(v);
sign = _PyLong_NonCompactSign(v);

unsigned long x = unroll_digits_ulong(v, &i);
while (--i >= 0) {
if (x > (ULONG_MAX >> PyLong_SHIFT)) {
*overflow = sign;
goto exit;
}
x = (x << PyLong_SHIFT) | v->long_value.ob_digit[i];
}
/* Haven't lost any bits, but casting to long requires extra
* care (see comment above).
*/
if (x <= (unsigned long)LONG_MAX) {
res = (long)x * sign;
}
else if (sign < 0 && x == PY_ABS_LONG_MIN) {
res = LONG_MIN;
}
else {
*overflow = sign;
/* res is already set to -1 */
}
UNROLL_DIGITS(v, ulong, long, unsigned long, ULONG_MAX, LONG);
goto exit;
fail:
*overflow = sign;
}
exit:
if (do_decref) {
Expand Down Expand Up @@ -701,7 +699,7 @@
Py_ssize_t
PyLong_AsSsize_t(PyObject *vv) {
PyLongObject *v;
Py_ssize_t i;
Py_ssize_t i, res = -1;
int sign;

if (vv == NULL) {
Expand All @@ -717,41 +715,35 @@
if (_PyLong_IsCompact(v)) {
return _PyLong_CompactValue(v);
}
i = _PyLong_DigitCount(v);
sign = _PyLong_NonCompactSign(v);

size_t x = unroll_digits_size_t(v, &i);
while (--i >= 0) {
if (x > (SIZE_MAX >> PyLong_SHIFT)) {
goto overflow;
}
x = (x << PyLong_SHIFT) | v->long_value.ob_digit[i];
}
/* Haven't lost any bits, but casting to a signed type requires
* extra care (see comment above).
*/
if (x <= (size_t)PY_SSIZE_T_MAX) {
return (Py_ssize_t)x * sign;
}
else if (sign < 0 && x == PY_ABS_SSIZE_T_MIN) {
return PY_SSIZE_T_MIN;
}
/* else overflow */

overflow:
UNROLL_DIGITS(v, size_t, Py_ssize_t, size_t, SIZE_MAX, PY_SSIZE_T);
return res;
fail:
PyErr_SetString(PyExc_OverflowError,
"Python int too large to convert to C ssize_t");
return -1;
return res;
}

#define UNROLL_UDIGITS(v, suff, utype, UMAX) \
do { \
Py_ssize_t i = _PyLong_DigitCount(v); \
size_t x = unroll_digits_##suff(v, &i); \
\
while (--i >= 0) { \
if (x > (UMAX >> PyLong_SHIFT)) { \
goto overflow; \
} \
x = (x << PyLong_SHIFT) | v->long_value.ob_digit[i]; \
} \
return x; \
} while (0);

/* Get a C unsigned long int from an int object.
Returns -1 and sets an error condition if overflow occurs. */

unsigned long
PyLong_AsUnsignedLong(PyObject *vv)
{
PyLongObject *v;
Py_ssize_t i;

if (vv == NULL) {
PyErr_BadInternalCall();
Expand Down Expand Up @@ -780,16 +772,7 @@
"can't convert negative value to unsigned int");
return (unsigned long) -1;
}
i = _PyLong_DigitCount(v);

unsigned long x = unroll_digits_ulong(v, &i);
while (--i >= 0) {
if (x > (ULONG_MAX >> PyLong_SHIFT)) {
goto overflow;
}
x = (x << PyLong_SHIFT) | v->long_value.ob_digit[i];
}
return x;
UNROLL_UDIGITS(v, ulong, unsigned long, ULONG_MAX);

Check warning on line 775 in Objects/longobject.c

View workflow job for this annotation

GitHub Actions / Windows / Build and test (x64) 

'return': conversion from 'size_t' to 'unsigned long', possible loss of data [D:\a\cpython\cpython\PCbuild\pythoncore.vcxproj]

Check warning on line 775 in Objects/longobject.c

View workflow job for this annotation

GitHub Actions / Windows (free-threading) / Build and test (x64) 

'return': conversion from 'size_t' to 'unsigned long', possible loss of data [D:\a\cpython\cpython\PCbuild\pythoncore.vcxproj]

Check warning on line 775 in Objects/longobject.c

View workflow job for this annotation

GitHub Actions / Windows / Build and test (arm64) 

'return': conversion from 'size_t' to 'unsigned long', possible loss of data [C:\a\cpython\cpython\PCbuild\pythoncore.vcxproj]

Check warning on line 775 in Objects/longobject.c

View workflow job for this annotation

GitHub Actions / Windows (free-threading) / Build and test (arm64) 

'return': conversion from 'size_t' to 'unsigned long', possible loss of data [C:\a\cpython\cpython\PCbuild\pythoncore.vcxproj]
overflow:
PyErr_SetString(PyExc_OverflowError,
"Python int too large to convert "
Expand All @@ -804,7 +787,6 @@
PyLong_AsSize_t(PyObject *vv)
{
PyLongObject *v;
Py_ssize_t i;

if (vv == NULL) {
PyErr_BadInternalCall();
Expand All @@ -824,18 +806,13 @@
"can't convert negative value to size_t");
return (size_t) -1;
}
i = _PyLong_DigitCount(v);
UNROLL_UDIGITS(v, size_t, size_t, SIZE_MAX);
overflow:
PyErr_SetString(PyExc_OverflowError,
"Python int too large to convert "
"to C size_t");
return (size_t) -1;

size_t x = unroll_digits_size_t(v, &i);
while (--i >= 0) {
if (x > (SIZE_MAX >> PyLong_SHIFT)) {
PyErr_SetString(PyExc_OverflowError,
"Python int too large to convert to C size_t");
return (size_t) -1;
}
x = (x << PyLong_SHIFT) | v->long_value.ob_digit[i];
}
return x;
}

/* Get a C unsigned long int from an int object, ignoring the high bits.
Expand Down Expand Up @@ -1731,7 +1708,7 @@
{
/* This version by Tim Peters */
PyLongObject *v;
long long res;
long long res = -1;
Py_ssize_t i;
int sign;
int do_decref = 0; /* if PyNumber_Index was called */
Expand All @@ -1756,11 +1733,9 @@
Py_ssize_t tmp = _PyLong_CompactValue(v);
if (tmp < LLONG_MIN) {
*overflow = -1;
res = -1;
}
else if (tmp > LLONG_MAX) {
*overflow = 1;
res = -1;
}
else {
res = (long long)tmp;
Expand All @@ -1770,30 +1745,11 @@
#endif
}
else {
i = _PyLong_DigitCount(v);
sign = _PyLong_NonCompactSign(v);
unsigned long long x = unroll_digits_ulong(v, &i);
while (--i >= 0) {
if (x > ULLONG_MAX >> PyLong_SHIFT) {
*overflow = sign;
res = -1;
goto exit;
}
x = (x << PyLong_SHIFT) + v->long_value.ob_digit[i];
}
/* Haven't lost any bits, but casting to long requires extra
* care (see comment above).
*/
if (x <= (unsigned long long)LLONG_MAX) {
res = (long long)x * sign;
}
else if (sign < 0 && x == PY_ABS_LLONG_MIN) {
res = LLONG_MIN;
}
else {
*overflow = sign;
res = -1;
}
UNROLL_DIGITS(v, ulong, long long, unsigned long long,
ULLONG_MAX, LLONG);
goto exit;
fail:
*overflow = sign;
}
exit:
if (do_decref) {
Expand Down
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