From a328071b520099fbdddd7867dd536d7e80925527 Mon Sep 17 00:00:00 2001
From: Ben Grant <benjamin.j.grant@gmail.com>
Date: Thu, 16 May 2024 11:37:46 -0700
Subject: [PATCH] add ziglang/zig#9703 reproduction

---
 checker.sh |  9 +++++++++
 repro.zig  | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+)
 create mode 100755 checker.sh
 create mode 100644 repro.zig

diff --git a/checker.sh b/checker.sh
new file mode 100755
index 0000000..3ae471e
--- /dev/null
+++ b/checker.sh
@@ -0,0 +1,9 @@
+#!/bin/bash
+
+zig build-exe repro.zig -O ReleaseSafe || exit 2
+./repro 2>&1 | grep inactive
+if [ $? -eq 0 ]; then
+	exit 0
+else
+	exit 2
+fi
diff --git a/repro.zig b/repro.zig
new file mode 100644
index 0000000..4d0cdb9
--- /dev/null
+++ b/repro.zig
@@ -0,0 +1,55 @@
+const std = @import("std");
+
+const SideData = union {
+    foo: u8,
+    bar: u8,
+};
+
+const Inst = struct {
+    func: Gadget,
+    data: SideData,
+};
+
+const Emulator = struct {
+    memory: [128]u8,
+    code: [64]Inst,
+    pc: u8 = 0,
+};
+
+const Gadget = *const fn (*Emulator, SideData) void;
+
+fn foo(emulator: *Emulator, side_data: SideData) void {
+    _ = emulator;
+    std.log.info("foo {}", .{side_data.foo});
+}
+
+fn bar(emulator: *Emulator, side_data: SideData) void {
+    _ = emulator;
+    _ = side_data;
+    @trap();
+}
+
+fn invalid(emulator: *Emulator, _: SideData) void {
+    _ = emulator;
+}
+
+fn decode(emulator: *Emulator, _: SideData) void {
+    const raw_instruction = std.mem.readInt(u16, emulator.memory[emulator.pc..][0..2], .big);
+    const inst: Inst = switch ((raw_instruction >> 8) & 0xf) {
+        0xf => .{ .func = &foo, .data = .{ .foo = @truncate(raw_instruction) } },
+        0xb => .{ .func = &bar, .data = .{ .bar = @truncate(raw_instruction) } },
+        else => .{ .func = &invalid, .data = undefined },
+    };
+    @call(.always_tail, inst.func, .{ emulator, inst.data });
+}
+
+pub fn main() void {
+    var emulator = Emulator{
+        .memory = undefined,
+        .code = undefined,
+    };
+    @memset(&emulator.code, .{ .func = &decode, .data = undefined });
+    const rom = [_]u8{ 0x0f, 0x23, 0x0b, 0x80 };
+    @memcpy(emulator.memory[0..rom.len], &rom);
+    emulator.code[emulator.pc].func(&emulator, emulator.code[emulator.pc].data);
+}