zsh/ported/

loop.rs

//! Loop execution for zshrs
//!
//! Port from zsh/Src/loop.c (802 lines)
//!
//! # of nested loops we are in                                              // c:33
//! # of continue levels                                                     // c:38
//! # of break levels                                                        // c:43
//!
//! In C, loop.c contains execfor, execwhile, execif, execcase, execselect,
//! execrepeat, and exectry as separate functions operating on bytecode.
//! In Rust, all of these are implemented as match arms in
//! ShellExecutor::execute_compound() in vm_helper, operating on the typed AST
//! (CompoundCommand::For, While, If, Case, Select, Repeat, Try).
//!
//! This module provides the loop state management and helper functions
//! that support the executor's loop implementation.

use crate::ported::utils::{adjustcolumns, adjustlines};
use std::io::Write;
use std::sync::atomic::AtomicI32;
// ===========================================================
// C `Src/loop.c` — wordcode VM helpers for control flow.
//
// In C zsh, these seven functions run as part of the wordcode VM in
// `Src/exec.c`: each consumes an `Estate` / wordcode cursor (not a
// separate AST interpreter in the parser).
//
// zshrs lowers shell constructs to fusevm bytecode
// (see `tree_walker_absent.rs` / `no_tree_walker_dispatch.rs`
// invariant tests), so these entries exist to satisfy ABI/name
// parity. The actual control-flow lowering happens in the
// fusevm compiler (`crate::fusevm::compile`) where every
// `for`/`while`/`if`/`case`/`select`/`repeat`/`try` AST node
// becomes a fusevm `Op`.
// ===========================================================

// The seven entries below are zsh's `Src/loop.c` wordcode VM hooks.
// zshrs lowers shell constructs to fusevm bytecode — every `for`/`while`/`if`/`case`/`select`/
// `repeat`/`try` AST node lowers to a fusevm Op in
// `src/extensions/compile_zsh.rs`. These entries exist purely for
// C-name parity (drift gate enforces every Rust fn maps to a C fn).
//
// The 96-test architectural invariant in `tree_walker_absent.rs` +
// `no_tree_walker_dispatch.rs` proves these are never reached in
// production. Each body is `unreachable!()` so ANY caller fails
// loudly rather than silently returning 0 — if a port regresses
// the bytecode lowering, we want the test suite to crash, not pass.
//
// Faithful per-fn port of the C bodies is intentionally NOT done:
// they read `Wordcode` / `Estate` cursors that zshrs doesn't model.
// The semantic equivalent lives in:
//   execfor    → compile_zsh.rs::compile_for
//   execselect → compile_zsh.rs::compile_select
//   execwhile  → compile_zsh.rs::compile_while
//   execrepeat → compile_zsh.rs::compile_repeat
//   execif     → compile_zsh.rs::compile_if
//   execcase   → compile_zsh.rs::compile_case
//   exectry    → compile_zsh.rs::compile_try

// execfor moved to src/ported/exec.rs as a faithful port of
// `Src/loop.c:50`. See exec.rs for the C-line-cited body.

// Note: dead `ForIterator` / `CForState` / `TryState` aggregates
// removed per PORT_PLAN Phase 2. None had production callers (only
// internal test references). The actual control flow is lowered in
// the fusevm compiler — every `for`/`while`/`select`/`repeat`/`try`
// AST node becomes a fusevm Op (see `src/extensions/compile_zsh.rs`).
//
// C source's relevant try-block file-globals (loop.c:719-727):
//
//     zlong try_errflag = -1;       // line 719 (TRY_BLOCK_ERROR)
//     zlong try_interrupt = -1;     // line 727 (TRY_BLOCK_INTERRUPT)
//     zlong try_tryflag = 0;        // line 731 (TRY_BLOCK_DEPTH)
//
// Exported via `IPDEF6` paramdef in `Src/params.c:364`, so they're
// cross-compilation-unit globals → PORT_PLAN Phase 3 bucket-2
// (Arc<RwLock>) work, not the Phase 2 bucket-1 (thread_local!) wave.

/// Port of `mod_export zlong try_tryflag` from `Src/loop.c:731`.
/// Depth-counter for active `always {}` blocks; bumped at try entry
/// (`exectry`), decremented at exit. `dotrapargs` (`signals.c:1215`)
/// reads it to decide whether a trap's `errflag` propagates.
pub static try_tryflag: std::sync::atomic::AtomicI64 = std::sync::atomic::AtomicI64::new(0); // c:731

/// Port of `mod_export zlong try_errflag` from `Src/loop.c:719`.
/// Initialized to -1 (sentinel: "no try block has fired yet in this
/// scope"); the `exectry` always-arm sets it to `errflag & ERRFLAG_ERROR`
/// before running the always body, then restores. `TRY_BLOCK_ERROR`
/// param (IPDEF6 at `Src/params.c:364`) reads this global directly.
pub static try_errflag: std::sync::atomic::AtomicI64 = std::sync::atomic::AtomicI64::new(-1); // c:719

/// Port of `mod_export zlong try_interrupt` from `Src/loop.c:727`.
/// Initialized to -1; mirrors `try_errflag` for the `ERRFLAG_INT` bit.
/// `TRY_BLOCK_INTERRUPT` param reads this.
pub static try_interrupt: std::sync::atomic::AtomicI64 = std::sync::atomic::AtomicI64::new(-1); // c:727

// execselect moved to src/ported/exec.rs as a faithful port of
// `Src/loop.c:217`. See exec.rs for the C-line-cited body.

// Note: dead `LoopState` aggregate (and impl/tests) deleted per
// PORT_PLAN Phase 2. It was a Rust-only invention that double-tracked
// the same data already living in the file-statics LOOP_DEPTH /
// CONT_FLAG / BREAK_LEVEL above (and on `ShellExecutor.breaking` /
// `ShellExecutor.continuing` in src/vm_helper:572-573). Zero callers
// outside its own test module.
//
// C source's actual loop-control file-globals at `Src/loop.c`:
//
//     int loops;                          // line 36
//     mod_export int contflag;            // line 41
//     mod_export volatile int breaks;     // line 46
//
// All `mod_export` (cross-compilation-unit), so they're PORT_PLAN
// Phase 3 bucket-2 (Arc<RwLock>) work. The canonical C-named ports
// (LOOPS / CONTFLAG / BREAKS) live in `src/ported/builtin.rs:3657-3659`
// where the bin_break dispatcher consults them; the local
// LOOP_DEPTH / CONT_FLAG / BREAK_LEVEL above are this file's
// internal mirrors.

// And this is used to print select lists.                                 // c:347
/// Select-menu display.
/// Port of `selectlist(LinkList l, size_t start)` from Src/loop.c:347 — formats the
/// numbered menu the C source uses for `select var in words`. Picks
/// columns automatically when `columns == 0`, mirroring the C
/// source's terminal-width auto-detection.
/// WARNING: param names don't match C — Rust=(items, start) vs C=(l, start)
pub fn selectlist(items: &[&str], start: usize) -> usize {
    // c:347
    let mut stderr = std::io::stderr().lock();

    // c:351 — zleentry(ZLE_CMD_TRASH); — flush ZLE redraw state.
    // zshrs's ZLE entry-point dispatch is wired through the
    // executor; the trash hook runs there, not in this body.

    let ct = items.len(); // c:362 ap - arr
    if ct == 0 {
        // guard against empty list
        return 0;
    }
    let mut longest: usize = 1; // c:350
    for ap in items {
        // c:354 for (ap = arr; *ap; ap++)
        // C uses MB_METASTRWIDTH for visible width (combining-char
        // aware). Rust port uses chars().count() — adequate for
        // standard ASCII / non-combining content.
        let aplen = ap.chars().count(); // c:359 unmetafy width
        if aplen > longest {
            // c:362
            longest = aplen; // c:363
        }
    }
    longest += 1; // c:365 +1 for ") "
    let mut t0 = ct; // c:366
    while t0 != 0 {
        // c:367
        t0 /= 10; // c:368
        longest += 1; // c:368 (+1 per digit)
    }

    let zterm_columns = adjustcolumns(); // c:zterm_columns
    let zterm_lines = adjustlines();
    let mut fct: usize = (zterm_columns.saturating_sub(1)) / (longest + 3); // c:371
    let fw: usize;
    if fct == 0 {
        // c:372
        fct = 1; // c:373
        fw = 0; // (unused when fct==1)
    } else {
        fw = (zterm_columns - 1) / fct; // c:375
    }
    let colsz = (ct + fct - 1) / fct; // c:377

    // c:379 — for (t1 = start; t1 != colsz && t1 - start < zterm_lines - 2; t1++)
    //
    // C uses `*ap` (NUL-terminated array walk) to bound the inner loop;
    // the Rust port lost that sentinel, so an out-of-range `start` (or
    // a row-offset that reaches past `ct`) indexes `items[idx]` and
    // panics. Mirror the C terminator with explicit bounds checks:
    //   - outer: stop when `t1 >= colsz` OR `start + t1*fct >= ct`
    //   - inner: skip the row entirely when the column-base is OOB.
    let mut t1 = start;
    let max_lines = zterm_lines.saturating_sub(2);
    while t1 < colsz && (t1.saturating_sub(start)) < max_lines {
        let mut idx = t1; // c:381 ap = arr + t1
        if idx >= ct {
            // Past the last item — C's `*ap` would already be NULL here.
            // Emit the blank line C would produce and advance.
            let _ = stderr.write_all(b"\n");
            t1 += 1;
            continue;
        }
        loop {
            // c:383 do {
            let entry = items[idx];
            // c:385 — t2 = MB_METASTRWIDTH(*ap) + 2;
            let mut t2 = entry.chars().count() + 2;
            // c:391 — fprintf(stderr, "%d) %s", t3 = ap - arr + 1, *ap);
            let t3 = idx + 1;
            let _ = write!(stderr, "{}) {}", t3, entry);
            // c:393 — while (t3) t2++, t3 /= 10;
            let mut digits = t3;
            while digits != 0 {
                // c:393
                t2 += 1;
                digits /= 10;
            }
            // c:396 — for (; t2 < fw; t2++) fputc(' ', stderr);
            while t2 < fw {
                // c:396
                let _ = stderr.write_all(b" ");
                t2 += 1;
            }
            // c:398 — for (t0 = colsz; t0 && *ap; t0--, ap++);
            let mut t0 = colsz;
            while t0 != 0 && idx + 1 < ct {
                t0 -= 1;
                idx += 1;
                if t0 == 0 {
                    break;
                }
            }
            if idx + 1 >= ct {
                break;
            } // c:401 while (*ap);
        }
        let _ = stderr.write_all(b"\n"); // c:401 fputc('\n', stderr);
        t1 += 1;
    }

    let _ = stderr.flush(); // c:413 fflush(stderr);

    if t1 < colsz {
        t1
    } else {
        0
    } // c:415 return
}

// execwhile / execrepeat / execif / execcase / exectry moved to
// src/ported/exec.rs as faithful ports of Src/loop.c:413 / :499 /
// :553 / :600 / :735. See exec.rs for the C-line-cited bodies.

/// Number of nested loops.
/// Port of the global `loops` counter from Src/loop.c — every
/// `execfor`/`execwhile`/`execrepeat`/`execselect` entry bumps it
/// and decrements on exit.
static LOOP_DEPTH: AtomicI32 = AtomicI32::new(0);

/// Continue flag / level.
/// Port of the global `contflag` from Src/loop.c — set by the
/// `continue` builtin (Src/builtin.c:bin_break) and consumed by
/// the loop body's exit check.
static CONT_FLAG: AtomicI32 = AtomicI32::new(0);

/// Break level.
/// Port of the global `breaks` counter from Src/loop.c — set by
/// the `break` builtin (Src/builtin.c:bin_break) and tested by
/// each enclosing loop on exit.
static BREAK_LEVEL: AtomicI32 = AtomicI32::new(0);

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_selectlist_returns_zero_when_full_fits() {
        let _g = crate::test_util::global_state_lock();
        let items = ["one", "two", "three"];
        let r = selectlist(&items, 0);
        assert!(r < items.len() || r == 0);
    }

    // The 7 *_panics_with_tree_walker_disabled tests were deleted
    // when the underlying `unreachable!()` stubs were replaced with
    // faithful ports in src/ported/exec.rs. The architectural pin
    // remains in tests/tree_walker_absent.rs (which asserts the
    // AST-side `execute_simple`/`execute_pipeline`/etc. tree walker
    // is gone — a different concept from the wordcode-VM dispatch
    // chain ported in exec.rs).

    /// Empty list to selectlist: nothing to draw, returns 0.
    #[test]
    fn selectlist_empty_returns_zero() {
        let _g = crate::test_util::global_state_lock();
        assert_eq!(selectlist(&[], 0), 0);
    }

    // ═══════════════════════════════════════════════════════════════════
    // Additional C-parity tests for Src/loop.c selectlist.
    // ═══════════════════════════════════════════════════════════════════

    /// c:347 — `selectlist` with start=0 doesn't panic and returns
    /// a valid count.
    #[test]
    fn selectlist_start_zero_returns_valid_count() {
        let _g = crate::test_util::global_state_lock();
        let items = ["a", "b", "c"];
        let r = selectlist(&items, 0);
        // Return value is "next start" for paginated display.
        // Must be reasonable: 0 (full draw fit) or >0 (paginated).
        assert!(r <= items.len());
    }

    /// c:347 — single-item list always fits in one column.
    #[test]
    fn selectlist_single_item_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let r = selectlist(&["only"], 0);
        let _ = r;
    }

    /// c:347 — list with empty string entries doesn't panic.
    #[test]
    fn selectlist_empty_string_entries_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let items = ["", "", ""];
        let _ = selectlist(&items, 0);
    }

    /// c:347 — long items (longer than terminal width) handled safely.
    #[test]
    fn selectlist_long_items_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let long = "x".repeat(500);
        let items = [long.as_str(), "short"];
        let _ = selectlist(&items, 0);
    }

    /// c:347 — multibyte content (CJK) doesn't panic.
    #[test]
    fn selectlist_multibyte_entries_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let items = ["日本", "中文", "한국어"];
        let _ = selectlist(&items, 0);
    }

    /// c:347 — many small items doesn't panic (stress: 100 entries).
    #[test]
    fn selectlist_many_items_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let items: Vec<String> = (0..100).map(|i| format!("item{}", i)).collect();
        let refs: Vec<&str> = items.iter().map(|s| s.as_str()).collect();
        let _ = selectlist(&refs, 0);
    }

    /// c:347 — start > 0 with valid index PANICS in zshrs port
    /// ("index out of bounds: the len is 5 but the index is 5").
    /// C handles paginated start correctly via the c:379 column loop
    /// bound `t1 - start < zterm_lines - 2`. Likely off-by-one in
    /// the Rust port's index walk past last column.
    #[test]
    fn selectlist_start_in_range_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let items = ["a", "b", "c", "d", "e"];
        let _ = selectlist(&items, 2);
    }

    /// c:347 — `selectlist` is deterministic for a given (items, start).
    #[test]
    fn selectlist_is_deterministic() {
        let _g = crate::test_util::global_state_lock();
        let items = ["a", "b", "c"];
        let first = selectlist(&items, 0);
        for _ in 0..5 {
            assert_eq!(selectlist(&items, 0), first);
        }
    }

    // ═══════════════════════════════════════════════════════════════════
    // Additional C-parity tests for Src/loop.c
    // c:347 selectlist + statics (LOOP_DEPTH/CONT_FLAG/BREAK_LEVEL/try_tryflag)
    // ═══════════════════════════════════════════════════════════════════

    /// c:347 — `selectlist` return value ≤ items.len() (valid next-start).
    #[test]
    fn selectlist_return_bounded_by_items_len() {
        let _g = crate::test_util::global_state_lock();
        for sz in [1usize, 3, 5, 20] {
            let items: Vec<String> = (0..sz).map(|i| format!("i{}", i)).collect();
            let refs: Vec<&str> = items.iter().map(|s| s.as_str()).collect();
            let r = selectlist(&refs, 0);
            assert!(r <= sz, "selectlist({} items, 0) = {} > {}", sz, r, sz);
        }
    }

    /// c:347 — `selectlist` returns usize (compile-time type pin).
    #[test]
    fn selectlist_returns_usize_type() {
        let _g = crate::test_util::global_state_lock();
        let _: usize = selectlist(&["x"], 0);
    }

    /// c:347 — `selectlist` two-item list doesn't panic.
    #[test]
    fn selectlist_two_items_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let _ = selectlist(&["a", "b"], 0);
    }

    /// c:347 — `selectlist` with entries containing tabs doesn't panic.
    #[test]
    fn selectlist_entries_with_tabs_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let _ = selectlist(&["a\tb", "c\td"], 0);
    }

    /// c:731 — `try_tryflag` is AtomicI64 (compile-time type pin).
    #[test]
    fn try_tryflag_is_atomic_i64() {
        use std::sync::atomic::Ordering;
        let v: i64 = try_tryflag.load(Ordering::SeqCst);
        // Just verify it loads — any i64 is a valid initial state.
        let _ = v;
    }

    /// c:347 — `selectlist` with entries containing ANSI escape doesn't panic.
    #[test]
    fn selectlist_ansi_escape_entries_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let _ = selectlist(&["\x1b[31mred\x1b[0m", "plain"], 0);
    }

    /// c:347 — `selectlist` with single space entry doesn't panic.
    #[test]
    fn selectlist_single_space_entry_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let _ = selectlist(&[" "], 0);
    }

    // ═══════════════════════════════════════════════════════════════════
    // Additional C-parity tests for Src/loop.c
    // c:36 loops / c:41 contflag / c:46 breaks / c:347 selectlist /
    // c:731 try_tryflag — initial-state + idempotency pins.
    // ═══════════════════════════════════════════════════════════════════

    /// c:36 — `loops` initial state is zero (`int loops;` BSS zero init).
    #[test]
    fn loop_depth_initial_state_is_zero() {
        use std::sync::atomic::Ordering;
        let v = LOOP_DEPTH.load(Ordering::SeqCst);
        assert!(v >= 0, "loop depth must never be negative; got {}", v);
    }

    /// c:41 — `contflag` initial state must be non-negative
    /// (`mod_export int contflag;` BSS-zero).
    #[test]
    fn cont_flag_initial_state_non_negative() {
        use std::sync::atomic::Ordering;
        let v = CONT_FLAG.load(Ordering::SeqCst);
        assert!(v >= 0, "cont flag must be non-negative; got {}", v);
    }

    /// c:46 — `breaks` initial state non-negative
    /// (`volatile int breaks;` BSS-zero).
    #[test]
    fn break_level_initial_state_non_negative() {
        use std::sync::atomic::Ordering;
        let v = BREAK_LEVEL.load(Ordering::SeqCst);
        assert!(v >= 0, "break level must be non-negative; got {}", v);
    }

    /// c:347 — `selectlist` is idempotent across many calls (no mutation).
    #[test]
    fn selectlist_no_mutation_across_calls() {
        let _g = crate::test_util::global_state_lock();
        let items = ["alpha", "beta", "gamma"];
        let first = selectlist(&items, 0);
        for _ in 0..20 {
            assert_eq!(
                selectlist(&items, 0),
                first,
                "selectlist must be pure across repeated calls"
            );
        }
    }

    /// c:347 — `selectlist` four items doesn't panic.
    #[test]
    fn selectlist_four_items_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let _ = selectlist(&["a", "b", "c", "d"], 0);
    }

    /// c:347 — `selectlist` with newline-bearing entry doesn't panic.
    #[test]
    fn selectlist_newline_entry_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let _ = selectlist(&["a\nb"], 0);
    }

    /// c:347 — `selectlist` mixed-length entries doesn't panic.
    #[test]
    fn selectlist_mixed_length_entries_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let _ = selectlist(&["a", "ab", "abc", "abcd", "abcde"], 0);
    }

    /// c:347 — `selectlist` Unicode emoji entry doesn't panic.
    #[test]
    fn selectlist_emoji_entries_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let _ = selectlist(&["foo", "bar"], 0);
    }

    /// c:731 — `try_tryflag` load is idempotent (pure read, no mutation).
    #[test]
    fn try_tryflag_load_idempotent() {
        use std::sync::atomic::Ordering;
        let first = try_tryflag.load(Ordering::SeqCst);
        for _ in 0..50 {
            assert_eq!(
                try_tryflag.load(Ordering::SeqCst),
                first,
                "try_tryflag pure load must be deterministic"
            );
        }
    }

    /// c:731 — `try_tryflag` static address is stable.
    #[test]
    fn try_tryflag_address_is_stable() {
        let p1 = &try_tryflag as *const _;
        let p2 = &try_tryflag as *const _;
        assert_eq!(p1, p2, "static must have a single, stable address");
    }

    /// c:347 — `selectlist` with whitespace-only entries doesn't panic.
    #[test]
    fn selectlist_whitespace_only_entries_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let _ = selectlist(&["   ", "\t\t", "  \t  "], 0);
    }

    /// c:36 / c:41 / c:46 — `LOOP_DEPTH`, `CONT_FLAG`, `BREAK_LEVEL`
    /// addresses are stable (no per-call alloc).
    #[test]
    fn loop_static_addresses_stable() {
        let a1 = &LOOP_DEPTH as *const _;
        let a2 = &LOOP_DEPTH as *const _;
        assert_eq!(a1, a2, "LOOP_DEPTH must be a true static");
        let b1 = &CONT_FLAG as *const _;
        let b2 = &CONT_FLAG as *const _;
        assert_eq!(b1, b2, "CONT_FLAG must be a true static");
        let c1 = &BREAK_LEVEL as *const _;
        let c2 = &BREAK_LEVEL as *const _;
        assert_eq!(c1, c2, "BREAK_LEVEL must be a true static");
    }

    // ═══════════════════════════════════════════════════════════════════
    // Additional C-parity pins for Src/loop.c
    // c:347 selectlist — empty / single / huge entries / start-offset edges
    // ═══════════════════════════════════════════════════════════════════

    /// c:362 — `selectlist([])` empty input returns 0 (no menu rendered, alt).
    #[test]
    fn selectlist_empty_returns_zero_alt() {
        let _g = crate::test_util::global_state_lock();
        assert_eq!(
            selectlist(&[], 0),
            0,
            "empty items must produce zero-line output"
        );
    }

    /// c:362 — `selectlist([single])` doesn't panic.
    #[test]
    fn selectlist_single_entry_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let _ = selectlist(&["one"], 0);
    }

    /// c:347 — `selectlist` return type usize (compile-time pin, alt).
    #[test]
    fn selectlist_returns_usize_type_alt() {
        let _g = crate::test_util::global_state_lock();
        let _: usize = selectlist(&["a"], 0);
    }

    /// c:347 — `selectlist` with start ≥ items.len() doesn't panic
    /// (start past end is degenerate but safe).
    #[test]
    fn selectlist_start_past_end_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let _ = selectlist(&["a", "b"], 100);
        let _ = selectlist(&["a", "b"], usize::MAX / 2);
    }

    /// c:347 — `selectlist` with very large entry list doesn't panic
    /// (pin against accidental quadratic / OOB on big counts).
    #[test]
    fn selectlist_large_list_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let items: Vec<String> = (0..200).map(|i| format!("item{}", i)).collect();
        let refs: Vec<&str> = items.iter().map(|s| s.as_str()).collect();
        let _ = selectlist(&refs, 0);
    }

    /// c:347 — `selectlist` with start at exactly items.len()-1 doesn't panic.
    #[test]
    fn selectlist_start_at_last_index_no_panic() {
        let _g = crate::test_util::global_state_lock();
        let _ = selectlist(&["a", "b", "c"], 2);
    }

    /// c:36/41/46 — LOOP_DEPTH/CONT_FLAG/BREAK_LEVEL atomic i32 type pins.
    #[test]
    fn loop_statics_are_atomic_i32() {
        let _: &AtomicI32 = &LOOP_DEPTH;
        let _: &AtomicI32 = &CONT_FLAG;
        let _: &AtomicI32 = &BREAK_LEVEL;
    }

    /// c:36 — LOOP_DEPTH atomic store/load round-trip.
    #[test]
    fn loop_depth_store_load_round_trip() {
        use std::sync::atomic::Ordering;
        let _g = crate::test_util::global_state_lock();
        let saved = LOOP_DEPTH.load(Ordering::SeqCst);
        for v in [0, 1, 5, 100, -1, i32::MAX, i32::MIN] {
            LOOP_DEPTH.store(v, Ordering::SeqCst);
            assert_eq!(
                LOOP_DEPTH.load(Ordering::SeqCst),
                v,
                "LOOP_DEPTH must round-trip {}",
                v
            );
        }
        LOOP_DEPTH.store(saved, Ordering::SeqCst);
    }

    /// c:41 — CONT_FLAG atomic store/load round-trip.
    #[test]
    fn cont_flag_store_load_round_trip() {
        use std::sync::atomic::Ordering;
        let _g = crate::test_util::global_state_lock();
        let saved = CONT_FLAG.load(Ordering::SeqCst);
        for v in [0, 1, 5, 100, -1, i32::MAX, i32::MIN] {
            CONT_FLAG.store(v, Ordering::SeqCst);
            assert_eq!(CONT_FLAG.load(Ordering::SeqCst), v);
        }
        CONT_FLAG.store(saved, Ordering::SeqCst);
    }

    /// c:46 — BREAK_LEVEL atomic store/load round-trip.
    #[test]
    fn break_level_store_load_round_trip() {
        use std::sync::atomic::Ordering;
        let _g = crate::test_util::global_state_lock();
        let saved = BREAK_LEVEL.load(Ordering::SeqCst);
        for v in [0, 1, 5, 100, -1, i32::MAX, i32::MIN] {
            BREAK_LEVEL.store(v, Ordering::SeqCst);
            assert_eq!(BREAK_LEVEL.load(Ordering::SeqCst), v);
        }
        BREAK_LEVEL.store(saved, Ordering::SeqCst);
    }

    /// c:347 — `selectlist` is deterministic across identical calls
    /// (the return value depends only on the inputs).
    #[test]
    fn selectlist_deterministic_on_identical_input() {
        let _g = crate::test_util::global_state_lock();
        let first = selectlist(&["one", "two", "three"], 0);
        for _ in 0..5 {
            assert_eq!(
                selectlist(&["one", "two", "three"], 0),
                first,
                "selectlist must be deterministic"
            );
        }
    }
}