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Hacktical C: practical hacker's guide to the C programming language

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218 points signa11 | 2 comments | 14 Apr 25 10:20 UTC | HN request time: 0s | source
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throwaway7894 ◴[14 Apr 25 13:39 UTC] No.43681154[source]▶

  #define hc_task_yield(task)   
  do {     
    task->state = __LINE__;   
    return;     
    case __LINE__:;           
  } while (0)
That's just diabolical. I would not have thought to write "case __LINE__". In the case of a macro, using __LINE__ twice expands to the same value where the macro is used, even if the macro has newlines. It makes sense, but TIL.
replies(5): >>43681327 #>>43681410 #>>43681515 #>>43681600 #>>43684691 #
1. gthompson512 ◴[14 Apr 25 14:17 UTC] No.43681600[source]▶
Minor correction, macros CANT have newlines, you need to splice them during preprocessing using \ followed by a new line, the actual code has these:

from https://github.com/codr7/hacktical-c/blob/main/macro/macro.h

#define hc_align(base, size) ({ \ __auto_type _base = base; \ __auto_type _size = hc_min((size), _Alignof(max_align_t)); \ (_base) + _size - ((ptrdiff_t)(_base)) % _size; \ }) \

After preprocessing it is a single line.

replies(1): >>43682532 #
2. fuhsnn ◴[14 Apr 25 15:40 UTC] No.43682532[source]▶
We might get multi-line macros in C2y standard: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3524.txt