Support ccall() for symengine and other libs

[Shaikh-Ubaid]

No description provided.

[Shaikh-Ubaid]

@anutosh491 It seems to work, but there is a catch.

$ cat integration_tests/symbolics_07.py                    
from lpython import ccall, CPtr
import os

@ccall(header="symengine/cwrapper.h", py_mod="symengine", py_mod_path=f"{os.environ['CONDA_PREFIX']}/lib")
def basic_new_heap() -> CPtr:
    pass

@ccall(header="symengine/cwrapper.h", py_mod="symengine", py_mod_path=f"{os.environ['CONDA_PREFIX']}/lib")
def basic_const_pi(x: CPtr) -> None:
    pass

@ccall(header="symengine/cwrapper.h", py_mod="symengine", py_mod_path=f"{os.environ['CONDA_PREFIX']}/lib")
def basic_str(x: CPtr) -> str:
    pass

def main0():
    x: CPtr = basic_new_heap()
    basic_const_pi(x)
    s: str = basic_str(x)
    print(s)
    # assert s == "pi"

main0()

$ python integration_tests/symbolics_07.py                    
b'pi'

$ lpython integration_tests/symbolics_07.py --enable-symengine --backend c
pi 

The outputs by lpython and cpython do not match. Therefore the assert in the integration_tests/symbolics_07.py fails (I temporarily commented it out).

[anutosh491]

I went through the example above and I think we get the b'pi' output through CPython while using ccall because ctypes library returns strings as bytes objects when calling C functions that return strings

[Shaikh-Ubaid]

I went through the example above and I think we get the b'pi' output through CPython while using ccall because ctypes library returns strings as bytes objects when calling C functions that return strings

Good catch @anutosh491! Thank you. I fixed it in lpython.py: Decode ctypes strings before returning.

[Shaikh-Ubaid]

Ready.

[anutosh491]

Good catch @anutosh491! Thank you. I fixed it in lpython.py: Decode ctypes strings before returning.

Yes , this seems to be the correct way to address this . Thank you

[certik]

I think that this looks great.

Thank you.

This can also be used in the LLVM and C backends when linking. Right now we ignore it and one has to link by hand, which is fine.