New Issue: [Bug]: Restore ability to export functions with arrays of C-style strings to Python

Notifications Issues
1

24874, "lydia-duncan", "[Bug]: Restore ability to export functions with arrays of C-style strings to Python", "2024-04-17T17:11:41Z"

Summary of Problem

Description:
Prior to the move from c_string to c_ptrConst(c_char), we were able to export functions that took arguments of type [ ] c_string. Unfortunately, we did not have a test of this in our testing system, so missed that the move to c_ptrConst(c_char) broke this functionality. We should (re-)enable array arguments with this element type.

Is this a blocking issue with no known work-arounds?
There are no work-arounds that allow you to modify the string array in both Python and Chapel, but it's not essential to what I'm working on.

If you want to return an array of strings from Chapel and send that as an argument to another exported function, I think you can use opaque arrays, but given that it tries to use an external array by default for this type you'd have to explicitly specify the opaque array type in some way.

Steps to Reproduce

Source Code:

Chapel file (foo.chpl):

use CTypes;

export proc takesArray(in x: [] c_ptrConst(c_char)) {
  for str in x {
    // Note: this assumes x will have initial contents
    writeln(string.createCopyingBuffer(str));
  }
}

export proc returnsArray(): [0..3] c_ptrConst(c_char) {
  var x: [0..3] c_ptrConst(c_char) = ["guess", "this", "could", "work?"];
  return x;
}

Python file (use_foo.py):

import foo

foo.chpl_setup()
x = foo.returnsArray()
foo.takesArray(x)
y = [b"maybe", b"this", b"also", b"works", b"too?"]
foo.takesArray(y)
foo.chpl_cleanup()

Compile command:
chpl --library-python foo.chpl

Execution command:
(note: need to make sure the location of the generated Python library is in your $PYTHONPATH)
python3 use_foo.py

Associated Future Test(s):
test/interop/python/cptrConstCharArrays.chpl #TBD

Configuration Information

  • Output of chpl --version: chpl version 2.1.0 pre-release
  • Output of $CHPL_HOME/util/printchplenv --anonymize: (should be almost any settings as long as CHPL_LIB_PIC=pic, though solving the problem for multilocale will probably involve additional steps)
    CHPL_TARGET_PLATFORM: darwin
    CHPL_TARGET_COMPILER: clang
    CHPL_TARGET_ARCH: x86_64
    CHPL_TARGET_CPU: native
    CHPL_LOCALE_MODEL: flat
    CHPL_COMM: none
    CHPL_TASKS: qthreads
    CHPL_LAUNCHER: none
    CHPL_TIMERS: generic
    CHPL_UNWIND: none
    CHPL_MEM: jemalloc
    CHPL_ATOMICS: cstdlib
    CHPL_GMP: none
    CHPL_HWLOC: bundled
    CHPL_RE2: bundled
    CHPL_LLVM: none *
    CHPL_AUX_FILESYS: none
    CHPL_LIB_PIC: pic
  • Back-end compiler and version, e.g. gcc --version or clang --version: any
  • (For Cray systems only) Output of module list: N/A