A hacky f*d up way to portably access errno from outside of C

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(in practice i can't imagine any reason SEEK_SET wouldn't be 0, but unnecessary fucked up hacks are fun so for now let's just pretend that any of this actually matters)

it's actually possible to work around this! lseek returns the new offset after seeking. so we can call lseek with an arbitrary whence value, and use the return value to determine whether it did what we wanted. if not, just repeat with different whence values until it works!

let i = 0; for (i <= 2; i += 1) { if (c_lseek(STDERR_FILENO, 0, i) == 0) { break; }; }; assert(i <= 2); defer c_lseek(STDERR_FILENO, 0, i);

i just loop from 0 to 2, because i figure that it'll probably always be one of those values. but there's no reason higher values couldn't also be checked.

conclusion

export fn main() void = { // demonstration: pass in -1 as the fd to cause EBADF match (write(-1, &0u8, 1)) { case size => abort(