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1801 :: passing function ptr from nim to C

• terry (orginal) [2015-11-14T00:48:35+01:00] view original

  I am using devel (SHA: f9ad735) and I am having trouble passing a pointer to nim function into C. Here is the code I am struggling with and this is the gcc errors:

  error: request for member 'ClPrc' in something not a structure or union
  error: 'TMP142' undeclared (first use in this function)
  error: request for member 'ClEnv' in something not a structure or union
  Run

  Which I traced the nim generated C code link here, it looks like this section is the culprit:

  memset((void*)(&LOC2), 0, sizeof(LOC2));
  LOC2.ClPrc = ((TMP142) (waitforawhile_95072)); LOC2.ClEnv = NIM_NIL;
  LOC3 = 0;
  LOC3 = uv_idle_start(pidle_95099, LOC2);
  Run

  I think nim should have just generated:

  LOC3 = uv_idle_start(pidle_95099, waitforawhile_95072);
  Run

  Can someone explain what I am doing wrong? I don't know what TMP142 and all this ClPrc / ClEnv is doing...

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• Araq (orginal) [2015-11-14T01:38:41+01:00] view original

  Common problem (and annoying the Nim compiler doesn't catch it), but proc type defaults to the .closure calling convention which is implemented as (fn, env) pair, incompatible with C. Use instead something like

  type MyCallback = proc (a, b: cint): cstring {.cdecl.}
  Run

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• terry (orginal) [2015-11-14T01:51:07+01:00] view original

  Awesome, that solved my problem. Thanks for responding so quickly.

  I am new to Nim so I am just starting to wrap my head around these pragmas. Looks like there are still alot of things about Nim that I need to learn.

  Have a good day!

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