[Pyrex] Interpreting error messages

[Edward C. Jones]

Matthias Baas wrote:

> At 10:17 27.04.2003 -0400, Edward C. Jones wrote:
>
>> The program is:
>>
>> #include <stdio.h>
>
>
> Remember that you're writing a Pyrex program, not a C program, so the 
> above line is a comment and is ignored by Pyrex.

If I am thinking C-like things, I tend to C-like programming. In Python 
I think Pythonically.
It is not easy to adopt a world view between the two. It would be easier 
if Pyrex was an extension of Python with optional strong typing which 
could read C header files and libraries.

>> cdef tostring(void* p):
>>     cdef char* s
>>     s = <char*> malloc(50*sizeof(char))
>>     sprintf(s, c"%p", p)
>>     return s
>>
>> The error messages are:
>>
>> /.../silly.pyx:5:8: Casting temporary Python object to non-Python type
>> /.../silly.pyx:6:22: Cannot convert 'void (*)' to Python object
>
Not very useful error messages. I would prefer the Python "undefined 
global variable" error.

>
> Since the "#include <stdio.h>" was just a comment and you didn't 
> declare malloc() and sprintf() Pyrex treats them as Python functions.
> Pyrex isn't able to read C header files yet, so you have to declare 
> the functions yourself, something like:
>
> cdef extern from "stdio.h":
>    void* malloc(int)
>    ...

This worked. Here is a trick I got from one of your recent postings:

cdef tostring(void* p):
    # Ugly. Cast a pointer to an int. Not portable.
    i = <int> p
    return "%x" % i