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Manipulating C pointers #546
Description
Here is an example of how pointers should be manipulated, in Fortran, Python, both should generate the same ASR, and the C backend should then generate the output below:
Fortran:
type(c_ptr) :: queries
integer(2), pointer :: x(:)
c_f_pointer(queries, x)
c_loc(x(idx))
Python:
from ltypes import c_loc, c_p_pointer, CPtr, Pointer
from typing import Annotate
queries: CPtr
x: Annotate[i16[:], Pointer]
x = c_p_pointer(queries, i16)
c_loc(x[idx])
C output:
void *queries;
int16_t *x;
x = (int16_t*)queries;
&x[idx];
Also allow passing void * pointers as arguments to functions.
Activity
certik commentedon Jun 1, 2022
To pass
void *as function arguments, in Python:translates to C:
certik commentedon Jun 1, 2022
Note: I think
c_loc(x[idx])will not work in CPython, sincex[idx]will return an integer as a value, so we can't take pointer to it from insidec_loc. We'll have to use some syntax from https://docs.python.org/3/library/ctypes.html#pointers.czgdp1807 commentedon Jun 7, 2022
In Python, instead of
x = c_p_pointer(queries, i16)can we do,c_p_pointer(queries, x)? @certikcertik commentedon Jun 8, 2022
Yes, that's fine, if it can be done.
certik commentedon Jun 15, 2022
Most of these are fixed. The remaining issue is #609.
ubaidsk commentedon Sep 9, 2023
Can this be done @certik , @czgdp1807 ? Probably not. I think
Pythondoes not allow/support updating a variable passed as argument.certik commentedon Sep 10, 2023
Right, Python does not support it.