Robert Bradshaw, 03.01.2012 03:00:
On Mon, Jan 2, 2012 at 5:48 PM, Lisandro Dalcin wrote:
On 2 January 2012 22:37, Mansour Moufid wrote:
Now my issue is as follows.
(I CCed the cython-users list if this question is more appropriate there.)
I have a simple file, int.pyx:
from libc.stdint cimport *
print long(UINT8_MAX)
print long(UINT16_MAX)
print long(UINT32_MAX)
print long(UINT64_MAX)
with the usual setup.py stuff. Compiling and running:
$ python setup.py build_ext --inplace
...
int.c:566:3: warning: overflow in implicit constant conversion [-Woverflow]
...
$ python -c 'import int'
255
65535
-1
-1
So obviously there are overflows here. Checking int.c, I see:
/* "int.pyx":2
* from libc.stdint cimport *
* print long(UINT8_MAX) #<<<<<<<<<<<<<<
* print long(UINT16_MAX)
* print long(UINT32_MAX)
*/
__pyx_t_1 = PyInt_FromLong(UINT8_MAX);
and so on...
PyInt_FromLong is used for all these constants, regardless of
signedness or width, so any argument larger than LONG_MAX overflows,
*before* being converted to the arbitrary-size Python integer type.
I don't know if this is a bug, or if I'm overlooking something. Is
there a way for me to use these constants with Python's arbitrary-size
integers?
All these constants are declared as "enum", so Cython promotes them to
"int". Once again, Cython should have something like a "const" type
qualifier to poperly declare these compile-time constants.
As workaround, you could explicitly cast the constants like this
"print long(<uint8_t>UINT8_MAX)"
I'm leaning towards declaring them as being the proper type to begin
with; what's to be gained by declaring these extern values as enums
(=const)? At least with the larger types we should do this to avoid
patently incorrect behavior, and this way they would be consistant
with the actual C for arithmetic promotion, etc.
+1
Stefan
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