// Foreign `-> [:0]u8` / `-> ?[:0]u8` returns: C hands back ONE `char *`;
// the fat sx string is synthesized at the call boundary ({ptr, strlen};
// NULL maps to the optional's null / an empty string) — issue 0128.
// Pre-fix, the call read the pointer register pair as {ptr, len} and the
// length was garbage (bus error on print).
#import "modules/std.sx";

libc :: #library "c";
err_text :: (code: i32) -> [:0]u8 #foreign libc "strerror";
sig_text :: (sig: i32) -> ?[:0]u8 #foreign libc "strsignal";
dlerror  :: () -> ?[:0]u8 #foreign libc;

main :: () -> i32 {
    // plain: strerror(0) = "Undefined error: 0" on macOS — assert shape,
    // not the exact text (locale/platform variance)
    t := err_text(2);
    if t.len < 5 { print("BUG: strerror too short ({})\n", t.len); return 1; }
    print("strerror(2) len ok\n");

    // optional, non-null branch
    o := sig_text(2);
    if o == null { print("BUG: strsignal null\n"); return 2; }
    if o!.len < 3 { print("BUG: strsignal too short\n"); return 3; }
    print("optional non-null ok\n");

    // optional, NULL branch: dlerror() with no pending error is NULL
    d := dlerror();
    if d != null { print("BUG: dlerror non-null\n"); return 4; }
    print("optional null ok\n");
    return 0;
}