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1608 :: cmdCount {.importc: "cmdCount".}: cint

• Stefan_Salewski (orginal) [2015-09-02T12:27:09+02:00] view original

  I know there are better options for command line parameters for Nim programs, like parseOpt ... But sometimes it is convenient to just use argc and argv as from C. So cmdCount and cmdLine are used in some wrappers, for example in the gtk2 we have:

  proc nim_init*() =
    var
      cmdLine{.importc: "cmdLine".}: array[0..255, cstring]
      cmdCount{.importc: "cmdCount".}: cint
    init(addr(cmdLine), addr(cmdCount))

  So I used it last night in a similar way, but got always 0 and nil as result. So I created this test program:

  #var # does work fine
  #  cmdCount {.importc: "cmdCount".}: cint
  #  cmdLine {.importc: "cmdLine".}: cstringArray # char**
  
  proc nux() =
    var # does not work
      cmdCount {.importc: "cmdCount".}: cint
      cmdLine {.importc: "cmdLine".}: cstringArray # char**
    
    echo cmdCount#, cmdLine[0]
    if  cmdLine == nil:
      echo "cmdLine == nil"
  
  nux()
  Run

  output is:

  $ ./ttt "aa" 1 bb
  0
  cmdLine == nil

  cmdCount and cmdLine seems to work only when defined outside of the proc. This is for Nim Compiler Version 0.11.3 (2015-08-11) [Linux: amd64].

  When defined in the proc, nimcache code is

  N_NIMCALL(void, nux_92003)(void) {
    int cmdCount;
    NCSTRING* cmdLine;
    NimStringDesc* LOC1;
    nimfr("nux", "ttt.nim")
    cmdCount = 0;
    cmdLine = 0;

  I guess that is indeed the intended behaviour. Maybe compiler should give a warning when using that syntax in a proc? And maybe some wrappers need fixes?

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• Jehan (orginal) [2015-09-02T12:49:06+02:00] view original

  You can work around this problem by using {.importc, global.}. Example:

  {.emit: """
  int foovar = 314;
  """.}
  
  proc main() =
    var foovar {.importc, global.}: cint
    echo foovar
  
  main()
  Run

  In the long term, it might be a good idea if {.importc.} implied global.

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