Mirror of forum.nim-lang.org

9009 :: Return cstringArray from C functions in Nim

• mros (orginal) [2022-03-14T14:59:10+01:00] view original

  I want to rewrite a C functions in Nim. This is the C signature:

  extern char **StringSplit(char sep, const char *str);
  Run

  I wrote this procedure:

  proc StringSplit*(sep: cchar, str: cstring): cstringArray {.cdecl, exportc.} =
      # something here
      
      return allocCstringArray(aStringsSeq)
  Run

  and all works as expected. My question is: where and when i call deallocCStringArray()?

---

• shirleyquirk (orginal) [2022-03-14T20:55:44+01:00] view original

  You'd call deallocCStringArray whenever you'd previously have free`d the pointer returned by your `StringSplit function.

---

• planetis (orginal) [2022-03-14T22:42:08+01:00] view original

  Make a copy with cstringArrayToSeq and free the original

---

• Araq (orginal) [2022-03-15T06:46:47+01:00] view original

  You don't have to rewrite the code in Nim, you can throw away your C code and use strutils.split.

---

• mros (orginal) [2022-03-15T07:16:02+01:00] view original

  I want to rewrite a C custom library in Nim to use in C code.

---

• mros (orginal) [2022-03-15T09:40:08+01:00] view original

  Do you mean something like this:

  nim impl:

  proc StringSplit*(): cstringArray {.cdecl, exportc.} =
      # something here
      return allocCstringArray(aStringsSeq)
  
  proc deallocA*(a: cstringArray) {.cdecl, exportc.} =
    deallocCStringArray(a)
  Run

  and C usage:

  extern char **StringSplit();
  extern void deallocA(char **arr);
  
  int main()
  {
     char **norder;
     norder = StringSplit();
     
     //  something here
     
     deallocA(norder);
     return 0;
  }
  Run

---