4 ms·

#define hc_task_yield(task) do { task->state = LINE; return; case LINE:; } while (0) That's just diabolical

#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.

veltas 1y ago
Credit to Simon Tatham https://www.chiark.greenend.org.uk/~sgtatham/coroutines.html https://www.chiark.greenend.org.uk/~sgtatham/coroutines.html
- makeset 1y ago
  I knew the name sounded familiar: Simon Tatham's Portable Puzzle Collection https://www.chiark.greenend.org.uk/~sgtatham/puzzles/ https://www.chiark.greenend.org.uk/~sgtatham/puzzles/
  - dwattttt 1y ago
    Also author of PuTTy
- quietbritishjim 1y ago
  > no commonly used high level language supports the coroutine call primitive Shows how old this post is. In fact I remember reading it well over 10 years ago, maybe more like 20. archive.org says that it's at least as old as 2001. A great article. I'm very excited to see he's published a new article on C++20 coroutines. I've read (or maybe skimmed...) a few introductions and not really got them, despite having used C# and Python coroutines a lot with no problems (even making changes to an async runtime for Python). Given how clear his C coroutine article is, I'm optimistic about the C++ article. > So, after the course, I went away and studied on my own, and wrote the introduction to C++ coroutines that I’d have liked to see. https://www.chiark.greenend.org.uk/~sgtatham/quasiblog/coroutines-c++20/ https://www.chiark.greenend.org.uk/~sgtatham/quasiblog/corou...
HeliumHydride 1y ago
With GNU extensions, you can make a simpler coroutine macro without switch/case abuse: #define CO_BEGIN static void* cr_state_ = &&cr_st_0; goto *cr_state_; cr_st_0: #define CO_RETURN(x) ({ __label__ resume; cr_state_ = &&resume; return (x); resume:; })
- deleted 1y ago
  [deleted]
- eqvinox 1y ago
  Whether this is "simpler"… debatable ;D
deleted 1y ago
[deleted]
gthompson512 1y ago
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 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.
- fuhsnn 1y ago
  We might get multi-line macros in C2y standard: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3524.txt https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3524.txt
tanelpoder 1y ago
I've written C on-and-off for over 30 years (just various throw-away prototypes and OS/app interaction microbenchmarks) and it took a while + a web search to get it. Diabolical indeed. Edit: And makes sense in hindsight.

#define hc_task_yield(task) do { task->state = __LINE__; return; case __LINE__:; } while (0) That's just diabolical

veltas 1y ago

Credit to Simon Tatham https://www.chiark.greenend.org.uk/~sgtatham/coroutines.html https://www.chiark.greenend.org.uk/~sgtatham/coroutines.html

makeset 1y ago
I knew the name sounded familiar: Simon Tatham's Portable Puzzle Collection https://www.chiark.greenend.org.uk/~sgtatham/puzzles/ https://www.chiark.greenend.org.uk/~sgtatham/puzzles/
- dwattttt 1y ago
  Also author of PuTTy
quietbritishjim 1y ago
> no commonly used high level language supports the coroutine call primitive Shows how old this post is. In fact I remember reading it well over 10 years ago, maybe more like 20. archive.org says that it's at least as old as 2001. A great article. I'm very excited to see he's published a new article on C++20 coroutines. I've read (or maybe skimmed...) a few introductions and not really got them, despite having used C# and Python coroutines a lot with no problems (even making changes to an async runtime for Python). Given how clear his C coroutine article is, I'm optimistic about the C++ article. > So, after the course, I went away and studied on my own, and wrote the introduction to C++ coroutines that I’d have liked to see. https://www.chiark.greenend.org.uk/~sgtatham/quasiblog/coroutines-c++20/ https://www.chiark.greenend.org.uk/~sgtatham/quasiblog/corou...

HeliumHydride 1y ago

With GNU extensions, you can make a simpler coroutine macro without switch/case abuse: #define CO_BEGIN static void* cr_state_ = &&cr_st_0; goto *cr_state_; cr_st_0: #define CO_RETURN(x) ({ __label__ resume; cr_state_ = &&resume; return (x); resume:; })

deleted 1y ago
[deleted]
eqvinox 1y ago
Whether this is "simpler"… debatable ;D

deleted 1y ago

[deleted]

gthompson512 1y ago

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 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.

fuhsnn 1y ago
We might get multi-line macros in C2y standard: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3524.txt https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3524.txt

tanelpoder 1y ago

I've written C on-and-off for over 30 years (just various throw-away prototypes and OS/app interaction microbenchmarks) and it took a while + a web search to get it. Diabolical indeed. Edit: And makes sense in hindsight.