fork(1) download
  1. #include <stdio.h>
  2.  
  3. #define PP_ARG_N( \
  4.   _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, \
  5.   _11, _12, _13, _14, _15, _16, _17, _18, _19, _20, \
  6.   _21, _22, _23, _24, _25, _26, _27, _28, _29, _30, \
  7.   _31, _32, _33, _34, _35, _36, _37, _38, _39, _40, \
  8.   _41, _42, _43, _44, _45, _46, _47, _48, _49, _50, \
  9.   _51, _52, _53, _54, _55, _56, _57, _58, _59, _60, \
  10.   _61, _62, _63, N, ...) N
  11.  
  12. #define PP_RSEQ_N() \
  13.   63, 62, 61, 60, \
  14.   59, 58, 57, 56, 55, 54, 53, 52, 51, 50, \
  15.   49, 48, 47, 46, 45, 44, 43, 42, 41, 40, \
  16.   39, 38, 37, 36, 35, 34, 33, 32, 31, 30, \
  17.   29, 28, 27, 26, 25, 24, 23, 22, 21, 20, \
  18.   19, 18, 17, 16, 15, 14, 13, 12, 11, 10, \
  19.   9, 8, 7, 6, 5, 4, 3, 2, 1, 0
  20.  
  21. #define PP_COMMASEQ_N() \
  22.   1, 1, 1, 1, \
  23.   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
  24.   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
  25.   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
  26.   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
  27.   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
  28.   1, 1, 1, 1, 1, 1, 1, 1, 0, 0
  29.  
  30. #define PP_COMMA() ,
  31.  
  32. #define PP_HASCOMMA(...) \
  33.   PP_NARG_(__VA_ARGS__, PP_COMMASEQ_N())
  34.  
  35. #define PP_NARG_HELPER1(a, b, N) \
  36.   PP_NARG_HELPER2(a, b, N)
  37. #define PP_NARG_HELPER2(a, b, N) \
  38.   PP_NARG_HELPER3_ ## a ## b(N)
  39. #define PP_NARG_HELPER3_01(N) 0
  40. #define PP_NARG_HELPER3_00(N) 1
  41. #define PP_NARG_HELPER3_11(N) N
  42.  
  43. #define PP_NARG_(...) PP_ARG_N(__VA_ARGS__)
  44.  
  45. #define PP_NARG(...) \
  46.   PP_NARG_HELPER1( \
  47.   PP_HASCOMMA(__VA_ARGS__), \
  48.   PP_HASCOMMA(PP_COMMA __VA_ARGS__ ()), \
  49.   PP_NARG_(__VA_ARGS__, PP_RSEQ_N()))
  50.  
  51. #define PP_ISZERO(x) \
  52.   PP_HASCOMMA(PP_ISZERO_HELPER_ ## x)
  53. #define PP_ISZERO_HELPER_0 ,
  54.  
  55. #define PP_PREPEND_NARG(...) \
  56.   PP_PREPEND_NARG_HELPER1(PP_NARG(__VA_ARGS__), __VA_ARGS__)
  57. #define PP_PREPEND_NARG_HELPER1(N, ...) \
  58.   PP_PREPEND_NARG_HELPER2(PP_ISZERO(N), N, __VA_ARGS__)
  59. #define PP_PREPEND_NARG_HELPER2(z, N, ...) \
  60.   PP_PREPEND_NARG_HELPER3(z, N, __VA_ARGS__)
  61. #define PP_PREPEND_NARG_HELPER3(z, N, ...) \
  62.   PP_PREPEND_NARG_HELPER4_ ## z (N, __VA_ARGS__)
  63. #define PP_PREPEND_NARG_HELPER4_1(N, ...) 0
  64. #define PP_PREPEND_NARG_HELPER4_0(N, ...) N, __VA_ARGS__
  65.  
  66. #define my_func(...) func(PP_PREPEND_NARG(__VA_ARGS__))
  67.  
  68. int func(int argc, ...)
  69. {
  70. printf("func() invoked with %d optional arguments\n", argc);
  71. return argc;
  72. }
  73.  
  74. int main()
  75. {
  76. my_func(1, 2);
  77. my_func(1);
  78. my_func();
  79. return 0;
  80. }
Success #stdin #stdout 0.01s 2680KB
stdin
Standard input is empty
stdout
func() invoked with 2 optional arguments
func() invoked with 1 optional arguments
func() invoked with 0 optional arguments