// issue-0024: NSLog/foreign-side-effect calls placed as the FIRST statement
// of an `if X { ... } else { ... }` branch body do not produce visible
// output, even when the branch is provably taken (the SECOND statement in
// the same body — also a foreign call — does produce output).
//
// ── Observed iOS-side symptom (session 59 bisect) ─────────────────────────
//
// In library/modules/gpu/metal.sx's `metal_create_texture_ios`:
//
//   slot : TextureSlot = .{ tex = tex, bytes_per_pixel = bytes_per_pixel };
//   self.textures.append(slot);
//   NSLog(ns_string("[metal] T6 appended\n".ptr));      // ← fires
//
//   pixels_null := pixels == null;
//   if pixels_null {
//       NSLog(ns_string("[metal] T6b null\n".ptr));     // ← never fires
//   } else {
//       NSLog(ns_string("[metal] T6a non-null\n".ptr)); // ← never fires
//       handle : u32 = xx self.textures.len;
//       metal_update_texture_region_ios(self, handle, 0, 0, w, h, pixels);
//                                                       //  ← DOES fire
//                                                       //    (its first
//                                                       //    NSLog at
//                                                       //    fn entry
//                                                       //    appears in
//                                                       //    the unified
//                                                       //    log)
//       NSLog(ns_string("[metal] T7 done\n".ptr));      // ← (helper crashed
//                                                       //    before this)
//   }
//
// T6 appears in the iOS unified log. T6a/T6b never appear. The else
// branch's helper call DOES fire (its own first-statement NSLog inside
// the helper appears). So the else-branch IS entered; just its first
// NSLog statement produces no output.
//
// ── Pure-sx repro below does NOT trigger ───────────────────────────────────
//
// Running `sx run examples/issue-0024.sx` exits 0 (counter == 4 — all
// bumps fired). The bug only manifests with foreign calls (NSLog / ns_string),
// and possibly only when the process subsequently crashes (replaceRegion
// in the metal.sx case) — which raises the alternative hypothesis that
// the missing NSLog output is just iOS unified-logging buffer-loss on
// process death, not a sx compiler bug. The runtime sequence between T6
// and the crash was ~500μs; logs within ~1ms of an unhandled exception
// can be lost to OSLog's internal buffering on Apple Silicon iOS-sim.
//
// ── Investigation plan ─────────────────────────────────────────────────────
//
// Two paths to disambiguate:
//   1. Replace NSLog markers with `write(STDERR_FILENO, ...)` calls
//      (synchronous, no OSLog involvement). If markers still don't appear:
//      sx compiler bug — likely in src/ir/lower.zig:2166-2196 (the
//      `is_value` branch of `lowerIfExpr` and downstream `lowerBlockValue`
//      around 922-948). Possible: side-effecting leading statements
//      dropped when branches are treated as values.
//   2. If markers DO appear with synchronous write: the iOS-side symptom
//      is unified-logging buffer-loss, not a compiler bug. Close this issue
//      as "wontfix — diagnostic limitation" and move the iOS debugging to
//      foreign-write tracing.
//
// ── Real-world impact ──────────────────────────────────────────────────────
//
// Bisecting issue-0026 (replaceRegion crash) is currently blocked: without
// trustworthy markers inside if/else branches we can't tell which arg
// arrives wrong. Resolution unblocks step 3b of the Metal port.

#import "modules/std.sx";

counter : s64 = 0;

bump :: () { counter = counter + 1; }

probe :: (skip: bool) {
    bump();
    if skip {
        bump();
        bump();
    } else {
        bump();
        bump();
    }
    bump();
}

main :: () -> s32 {
    probe(false);
    // counter == 4 (entry + 2 in false branch + exit) → exit 0
    if counter == 4 then 0 else 1;
}