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8555 :: Basic nimterop usage for simple c++ struct?

• ggibson (orginal) [2021-10-28T18:20:26+02:00] view original

  • I'm wrapping some simple c++ code
  • I have manual wrapping experience, but am trying to learn nimterop so I can scale to wrapping larger codebases
  • I'm reading the nimterop docs and API for cimport
  • nimterop seems to break for a simple struct with a vector

  Questions:

  • What's the recommended workflow here?
  • Can you recommend any good examples of nimterop usage?

  My MWE:

  // sample.h
  #include <vector>
  struct SimpleStruct {
    std::vector<double> rewards;
  };
  void useStruct();
  Run

  // sample.cpp
  #include "sample.h"
  void useStruct() {
    SimpleStruct st;
    st.rewards = {1,3,5};
  }
  Run

  import nimterop/cimport
  static:
    cDebug()
    cDisableCaching()
  cCompile(path="sample.cpp", mode="cpp")
  cImport(filename="sample.h", mode="cpp")
  echo "finished"
  Run

  Output shows struct field confusion

  {.push hint[ConvFromXtoItselfNotNeeded]: off.}
  
  
  {.pragma: impsampleHdr, header: "<full_path...>/sample.h".}
  {.experimental: "codeReordering".}
  {.compile: "<full_path...>/sample.cpp".}
  type
    SimpleStruct* {.bycopy, impsampleHdr, importc: "struct SimpleStruct".} = object
      a1*: rewards
  
  proc useStruct*() {.importc, cdecl, impsampleHdr.}
  {.pop.}
  Run

  Error

  
  <...> template/generic instantiation of `cImport` from here
  Error: undeclared identifier: 'rewards'
  Run

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• Araq (orginal) [2021-10-28T19:19:02+02:00] view original

  I don't know if nimterop supports C++. c2nim does support C++.

---

• ynfle (orginal) [2021-10-28T19:20:52+02:00] view original

  You have a field in your nim type object that is of type rewards. You haven't declared such a type.

  I'm pretty sure you can just use importc and let it do the rest, you don't have to declare the fields etc.

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• ggibson (orginal) [2021-10-28T19:45:21+02:00] view original

  @ynfle Yes, but I didn't write that. This is the problem.

  @Araq, ah okay, I'll use c2nim. Thank you for the direction. So far I'm struggling even installing c2nim. I wonder if c2nim does not work yet with v1.6? I'll poke at it some more.

  
  > nimble update
  ...
  › nimble install c2nim
  Downloading https://github.com/nim-lang/c2nim using git
    Verifying dependencies for [email protected]
  tables.nim(234)          raiseKeyError
  Error: unhandled exception: key not found: url [KeyError]
  
  › nimble install c2nim@#head
  Downloading https://github.com/nim-lang/c2nim using git
    Verifying dependencies for c2nim@#head
  tables.nim(234)          raiseKeyError
  Error: unhandled exception: key not found: url [KeyError]
  
  › nimble --version
  nimble v0.13.1 compiled at 2021-10-23 01:24:00
  git hash: d13f3b8ce288b4dc8c34c219a4e050aaeaf43fc9
  
  › nim --version
  Nim Compiler Version 1.6.0 [Linux: amd64]
  Compiled at 2021-10-23
  Copyright (c) 2006-2021 by Andreas Rumpf
  
  git hash: 727c6378d2464090564dbcd9bc8b9ac648467e38
  active boot switches: -d:release
  Run

---

• Araq (orginal) [2021-10-28T19:51:52+02:00] view original

  Try this:

  
  git clone https://github.com/nim-lang/c2nim
  cd c2nim
  nim c c2nim
  cp c2nim somewhere_in_your_$PATH
  Run

  c2nim has no dependencies anyway, no need to bother Nimble with it.

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