Cannot convert 'int8_t *' to Python object
Bottiger
types.
However, it seems that Cython can only convert python objects to
"char*", even when the typedef is the same type as char*.
.....
cdef extern from "header.h":
void prototype(int8_t*)
def test(pystring):
prototype(pystring)
Cannot convert 'int8_t *' to Python Object
...
cdef extern from "header.h":
ctypedef char int8_t
void prototype(int8_t*)
def test(pystring):
prototype(pystring)
Cannot convert 'int8_t *' to Python Object
What am I doing wrong?
Stefan Behnel
> I am using "from libc.stdint cimport *" to get fixed width integer
> types.
Regarding this bit, I just noticed that all integer types are simply
ctypedef'ed to int in that file:
ctypedef signed int int8_t
ctypedef signed int int16_t
ctypedef signed int int32_t
ctypedef signed int int64_t
ctypedef unsigned int uint8_t
ctypedef unsigned int uint16_t
ctypedef unsigned int uint32_t
ctypedef unsigned int uint64_t
Wouldn't it make more sense to typedef them to something with a closer
match to the integer types that Cython knows, i.e. byte/8, short/16,
int/32, long/64?
> However, it seems that Cython can only convert python objects to
> "char*", even when the typedef is the same type as char*.
Well, it won't convert *most* pointer types to Python objects
automatically, with (s/u)char* being the only special cased exception. But
you can use an explicit cast.
> cdef extern from "header.h":
> ctypedef char int8_t
> void prototype(int8_t*)
>
> def test(pystring):
> prototype(pystring)
>
> Cannot convert 'int8_t *' to Python Object
Try
prototype(<char*>pystring)
instead to get automatic conversion from a byte string to a char*, which
Cython should then be able to assign to a ctypedef'ed int8_t*.
BTW, note that this only handles byte strings, unicode strings require
explicit encoding.
Stefan
Bottiger
But now I have another library which has
prototype(uint8_t*)
prototype(<char*>pystring)
and when I use that trick, it says
Cannot assign type 'char *' to 'uint8_t *'
Is there any way to fix this?
Lisandro Dalcin
> Ok it works that way.
>
> But now I have another library which has
>
> prototype(uint8_t*)
> prototype(<char*>pystring)
>
> and when I use that trick, it says
>
> Cannot assign type 'char *' to 'uint8_t *'
>
> Is there any way to fix this?
>
prototype(<int8_t*>(<char*>pystring))
--
Lisandro Dalcin
---------------
CIMEC (INTEC/CONICET-UNL)
Predio CONICET-Santa Fe
Colectora RN 168 Km 472, Paraje El Pozo
Tel: +54-342-4511594 (ext 1011)
Tel/Fax: +54-342-4511169
Stefan Behnel
> On 5 September 2010 18:51, Bottiger wrote:
>> Ok it works that way.
>>
>> But now I have another library which has
>>
>> prototype(uint8_t*)
>> prototype(<char*>pystring)
>>
>> and when I use that trick, it says
>>
>> Cannot assign type 'char *' to 'uint8_t *'
>>
>> Is there any way to fix this?
>>
>
> prototype(<int8_t*>(<char*>pystring))
I'd try this first:
prototype(<unsigned char*>pystring)
Stefan
Lisandro Dalcin
Cython has stricter typing than C, more or less like to C++, you have to:
prototype(<int8_t*>(<unsigned char*>pystring))
Robert Bradshaw
> Bottiger, 05.09.2010 07:30:
>>
>> I am using "from libc.stdint cimport *" to get fixed width integer
>> types.
>
> Regarding this bit, I just noticed that all integer types are simply
> ctypedef'ed to int in that file:
>
> ctypedef signed int int8_t
> ctypedef signed int int16_t
> ctypedef signed int int32_t
> ctypedef signed int int64_t
> ctypedef unsigned int uint8_t
> ctypedef unsigned int uint16_t
> ctypedef unsigned int uint32_t
> ctypedef unsigned int uint64_t
>
> Wouldn't it make more sense to typedef them to something with a closer match
> to the integer types that Cython knows, i.e. byte/8, short/16, int/32,
> long/64?
It really doesn't matter, as it completely ignores the defined
longness and generates code based on the actual longness.
- Robert
Lisandro Dalcin
Well, for integer promotion rules it does matter, right?
Robert Bradshaw
> On 6 September 2010 12:55, Robert Bradshaw <robe...@math.washington.edu> wrote:
>> On Sun, Sep 5, 2010 at 1:46 AM, Stefan Behnel <stef...@behnel.de> wrote:
>>> Bottiger, 05.09.2010 07:30:
>>>>
>>>> I am using "from libc.stdint cimport *" to get fixed width integer
>>>> types.
>>>
>>> Regarding this bit, I just noticed that all integer types are simply
>>> ctypedef'ed to int in that file:
>>>
>>> ctypedef signed int int8_t
>>> ctypedef signed int int16_t
>>> ctypedef signed int int32_t
>>> ctypedef signed int int64_t
>>> ctypedef unsigned int uint8_t
>>> ctypedef unsigned int uint16_t
>>> ctypedef unsigned int uint32_t
>>> ctypedef unsigned int uint64_t
>>>
>>> Wouldn't it make more sense to typedef them to something with a closer match
>>> to the integer types that Cython knows, i.e. byte/8, short/16, int/32,
>>> long/64?
>>
>> It really doesn't matter, as it completely ignores the defined
>> longness and generates code based on the actual longness.
>>
>
> Well, for integer promotion rules it does matter, right?
Sorry, yes, it does there. I was only thinking about conversion, so
yes, we should fix that (and bite the bullet that we can't be
right...).
- Robert
Lisandro Dalcin
Should we follow LP64?
Robert Bradshaw
Yes, that model makes the most sense to use.
- Robert