Andy WingoMar 13

me: i wish we could have tail calls in c
gcc: we have tail calls at home
the tail calls:

https://godbolt.org/z/GT5PvnxP9

Show threadAndy WingoMar 13
a kind person shares this powerful incantation: `if (1) [[gnu::musttail]]` https://godbolt.org/z/f8fzf9b5M
Compiler Explorer - C (x86-64 gcc 15.2)

int f(void); static int g(void) { return f(); return 11; } static int h(void) { if (1) [[gnu::musttail]] return f(); return 42; }

Show threadAndy WingoMar 13
lol gcc's tail call implementation is extraordinarily squirrely, it happily inlines functions that do tail calls but then dies because it fails to turn the inlined tail calls into regular calls. (clang fails in different ways :P)
Show threadAndy WingoMar 13
"cannot tail-call: other reasons" this energy is sending meeeeee, the compiler has determined that it is friday
Show threadvoid friendMar 13
@wingo I see why you liked the if (1)… Good luck with the tail calls.
Show threadAndy WingoMar 13
@void_friend fwiw, i got it to work if i __attribute__((noinline)) the functions that make tail calls 😅
Show threadvoid friendMar 13
@wingo Why doesn't enabling the tail-call optimization for the entire compilation unit work for you? You're already targeting a GCC-like compiler anyway, surely you're compiling the C file yourself or can tell the person who will compile it to use -foptimize-sibling-calls (I think the option is)?
Show threadvoid friend
@wingo Also, I wonder if you could implement tail calls in standard C from longjmp (pls do not implement tail calls from longjmp)
Mar 13 at 11:19amWeb