calcit 0.12.32

Interpreter and js codegen for Calcit
Documentation
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
use crate::runner;
use cirru_edn::Edn;
use colored::Colorize;
use std::collections::HashMap;
use std::path::{Path, PathBuf};
use std::process;
use std::sync::atomic::AtomicUsize;
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::{Arc, LazyLock, Mutex};
use std::thread;
use std::time::Instant;

use calcit::{
  builtins,
  builtins::{RegisteredProcDescriptor, RegisteredProcPlatform, RegisteredProcStability},
  calcit::{Calcit, CalcitErr, CalcitErrKind},
  call_stack::{CallStackList, display_stack},
  data::edn::{calcit_to_edn, edn_to_calcit, sanitize_edn_for_format},
  runner::track,
};

/// FFI protocol types
type EdnFfi = fn(args: Vec<Edn>) -> Result<Edn, String>;
type EdnFfiFn = fn(
  args: Vec<Edn>,
  f: Arc<dyn Fn(Vec<Edn>) -> Result<Edn, String> + Send + Sync + 'static>,
  finish: Arc<dyn FnOnce()>,
) -> Result<Edn, String>;

/// lazily cache dylibs, in case Linux drops memory of libraries
static DYLIBS: LazyLock<Mutex<HashMap<String, Arc<libloading::Library>>>> = LazyLock::new(|| Mutex::new(HashMap::new()));
static TRACE_FFI: AtomicBool = AtomicBool::new(false);
static TRACE_FFI_EVENT_ID: AtomicUsize = AtomicUsize::new(1);
static TRACE_FFI_STARTED: LazyLock<Instant> = LazyLock::new(Instant::now);

#[allow(dead_code)]
pub fn set_trace_ffi(v: bool) {
  TRACE_FFI.store(v, Ordering::Relaxed);
  if v {
    let edn_version = cirru_edn::version();
    let cwd = std::env::current_dir()
      .map(|p| p.display().to_string())
      .unwrap_or_else(|_| "<unknown-cwd>".to_string());
    let exe = std::env::current_exe()
      .map(|p| p.display().to_string())
      .unwrap_or_else(|_| "<unknown-exe>".to_string());
    trace_ffi_event(
      "enable",
      format!(
        "cwd={cwd} exe={exe} abi={ABI_VERSION} edn={edn_version} host={}",
        std::env::consts::OS
      ),
    );
  }
}

fn should_trace_ffi() -> bool {
  TRACE_FFI.load(Ordering::Relaxed)
}

fn format_edn_args_for_trace(args: &[Edn]) -> String {
  let sanitized: Vec<Edn> = args.iter().map(sanitize_edn_for_format).collect();
  match cirru_edn::format(&Edn::List(cirru_edn::EdnListView(sanitized)), true) {
    Ok(s) => s.trim().to_owned(),
    Err(e) => format!("<failed to format ffi args: {e}>"),
  }
}

fn resolve_trace_path(lib_name: &str) -> String {
  let path = Path::new(lib_name);
  let resolved: PathBuf = if path.is_absolute() {
    path.to_path_buf()
  } else {
    std::env::current_dir().unwrap_or_else(|_| PathBuf::from(".")).join(path)
  };

  match resolved.canonicalize() {
    Ok(p) => p.display().to_string(),
    Err(_) => resolved.display().to_string(),
  }
}

fn trace_ffi_event(label: &str, message: impl AsRef<str>) {
  if should_trace_ffi() {
    let event_id = TRACE_FFI_EVENT_ID.fetch_add(1, Ordering::Relaxed);
    let elapsed_ms = TRACE_FFI_STARTED.elapsed().as_secs_f64() * 1000.0;
    eprintln!(
      "[ffi #{event_id} +{elapsed_ms:.3}ms pid={} tid={:?}] {label} {}",
      process::id(),
      thread::current().id(),
      message.as_ref()
    );
  }
}

/// load dylib, cache it
fn load_dylib(lib_name: &str) -> Result<Arc<libloading::Library>, CalcitErr> {
  let resolved_path = resolve_trace_path(lib_name);
  let mut dylibs = DYLIBS
    .lock()
    .map_err(|_| CalcitErr::use_str(CalcitErrKind::Unexpected, "failed to lock dylib cache"))?;
  if let Some(lib) = dylibs.get(lib_name) {
    trace_ffi_event("reuse-dylib", format!("lib={lib_name} resolved={resolved_path}"));
    return Ok(lib.to_owned());
  }
  trace_ffi_event("load-dylib", format!("lib={lib_name} resolved={resolved_path}"));
  let lib = unsafe { libloading::Library::new(lib_name) }
    .map_err(|e| CalcitErr::use_str(CalcitErrKind::Unexpected, format!("failed to load dylib `{lib_name}`: {e}")))?;
  let lib = Arc::new(lib);
  dylibs.insert(lib_name.to_owned(), lib.to_owned());
  Ok(lib)
}

fn ensure_abi_compatible(lib: &libloading::Library, lib_name: &str) -> Result<(), CalcitErr> {
  let expected_edn_version = cirru_edn::version();
  trace_ffi_event("lookup-abi", format!("lib={lib_name}"));
  let lookup_version: libloading::Symbol<fn() -> String> = unsafe { lib.get("abi_version".as_bytes()) }.map_err(|e| {
    CalcitErr::use_str(
      CalcitErrKind::Unexpected,
      format!("failed to lookup `abi_version` in `{lib_name}`: {e}"),
    )
  })?;
  let current = lookup_version();
  trace_ffi_event("abi-version", format!("lib={lib_name} current={current} expected={ABI_VERSION}"));
  if current != ABI_VERSION {
    return CalcitErr::err_str(CalcitErrKind::Unexpected, format!("ABI versions mismatch: {current} {ABI_VERSION}")).map(|_| ());
  }

  trace_ffi_event("lookup-edn-version", format!("lib={lib_name}"));
  let lookup_edn_version: libloading::Symbol<fn() -> String> = unsafe { lib.get("edn_version".as_bytes()) }.map_err(|e| {
    CalcitErr::use_str(
      CalcitErrKind::Unexpected,
      format!("failed to lookup `edn_version` in `{lib_name}`: {e}"),
    )
  })?;
  let current_edn = lookup_edn_version();
  trace_ffi_event(
    "edn-version",
    format!("lib={lib_name} current={current_edn} expected={expected_edn_version}"),
  );
  if current_edn != expected_edn_version {
    return CalcitErr::err_str(
      CalcitErrKind::Unexpected,
      format!("cirru_edn versions mismatch: {current_edn} {expected_edn_version}"),
    )
    .map(|_| ());
  }
  Ok(())
}

const ABI_VERSION: &str = "0.0.9";

pub fn inject_platform_apis() {
  builtins::register_import_proc_with_descriptor(
    "&call-dylib-edn",
    call_dylib_edn,
    RegisteredProcDescriptor {
      arity_min: 2,
      arity_max: None,
      platforms: vec![RegisteredProcPlatform::Native],
      stability: RegisteredProcStability::Public,
      docs_hint: Some(Arc::from("Fix: use native runtime and pass (lib-name method ...args).")),
      callback_last: false,
    },
  );
  builtins::register_import_proc("echo", stdout_println);
  builtins::register_import_proc("println", stdout_println);
  builtins::register_import_proc("eprintln", stderr_println);
  builtins::register_import_proc_with_descriptor(
    "&call-dylib-edn-fn",
    call_dylib_edn_fn,
    RegisteredProcDescriptor {
      arity_min: 3,
      arity_max: None,
      platforms: vec![RegisteredProcPlatform::Native],
      stability: RegisteredProcStability::Public,
      docs_hint: Some(Arc::from("Fix: use native runtime and put callback fn as last argument.")),
      callback_last: true,
    },
  );
  builtins::register_import_proc_with_descriptor(
    "&blocking-dylib-edn-fn",
    blocking_dylib_edn_fn,
    RegisteredProcDescriptor {
      arity_min: 3,
      arity_max: None,
      platforms: vec![RegisteredProcPlatform::Native],
      stability: RegisteredProcStability::Public,
      docs_hint: Some(Arc::from("Fix: use native runtime and put callback fn as last argument.")),
      callback_last: true,
    },
  );
  builtins::register_import_proc("async-sleep", builtins::meta::async_sleep);
  builtins::register_import_proc("on-control-c", on_ctrl_c);
  if !calcit::quiet_tool_output() {
    eprintln!("{}", "registered platform APIs".dimmed());
  }
}

// &call-dylib-edn
pub fn call_dylib_edn(xs: Vec<Calcit>, _call_stack: &CallStackList) -> Result<Calcit, CalcitErr> {
  if xs.len() < 2 {
    return CalcitErr::err_str(CalcitErrKind::Arity, format!("&call-dylib-edn expected >2 arguments, got: {xs:?}"));
  }
  let lib_name: String = if let Calcit::Str(s) = &xs[0] {
    (**s).to_owned()
  } else {
    return CalcitErr::err_str(CalcitErrKind::Type, format!("&call-dylib-edn expected a lib_name, got: {}", xs[0]));
  };

  let method: String = if let Calcit::Str(s) = &xs[1] {
    (**s).to_owned()
  } else {
    return CalcitErr::err_str(
      CalcitErrKind::Type,
      format!("&call-dylib-edn expected a method name, got: {}", xs[1]),
    );
  };
  let mut ys: Vec<Edn> = Vec::with_capacity(xs.len());
  for v in xs.into_iter().skip(2) {
    ys.push(calcit_to_edn(&v)?);
  }

  trace_ffi_event(
    "call",
    format!(
      "lib={lib_name} resolved={} symbol={method} argc={} args={}",
      resolve_trace_path(&lib_name),
      ys.len(),
      format_edn_args_for_trace(&ys)
    ),
  );

  let lib = load_dylib(&lib_name)?;
  ensure_abi_compatible(&lib, &lib_name)?;
  trace_ffi_event("lookup-symbol", format!("lib={lib_name} symbol={method}"));
  let func: libloading::Symbol<EdnFfi> = unsafe { lib.get(method.as_bytes()) }.map_err(|e| {
    CalcitErr::use_str(
      CalcitErrKind::Unexpected,
      format!("failed to load FFI symbol `{method}` in `{lib_name}`: {e}"),
    )
  })?;
  let ret = func(ys.to_owned()).map_err(|e| {
    trace_ffi_event("error", format!("lib={lib_name} symbol={method} {e}"));
    e
  })?;
  trace_ffi_event(
    "return",
    format!(
      "lib={lib_name} symbol={method} ret={}",
      format_edn_args_for_trace(std::slice::from_ref(&ret))
    ),
  );
  Ok(edn_to_calcit(&ret, &Calcit::Nil))
}

pub fn stdout_println(xs: Vec<Calcit>, _call_stack: &CallStackList) -> Result<Calcit, CalcitErr> {
  let mut s = String::from("");
  for (idx, x) in xs.into_iter().enumerate() {
    if idx > 0 {
      s.push(' ');
    }
    s.push_str(&x.turn_string());
  }
  println!("{s}");
  Ok(Calcit::Nil)
}

pub fn stderr_println(xs: Vec<Calcit>, _call_stack: &CallStackList) -> Result<Calcit, CalcitErr> {
  let mut s = String::from("");
  for (idx, x) in xs.into_iter().enumerate() {
    if idx > 0 {
      s.push(' ');
    }
    s.push_str(&x.turn_string());
  }
  eprintln!("{s}");
  Ok(Calcit::Nil)
}

/// pass callback function to FFI function, so it can call multiple times
/// currently for HTTP servers
pub fn call_dylib_edn_fn(xs: Vec<Calcit>, call_stack: &CallStackList) -> Result<Calcit, CalcitErr> {
  if xs.len() < 3 {
    return CalcitErr::err_str(
      CalcitErrKind::Arity,
      format!("&call-dylib-edn-fn expected >3 arguments, got: {xs:?}"),
    );
  }

  let lib_name: String = if let Calcit::Str(s) = &xs[0] {
    (**s).to_owned()
  } else {
    return CalcitErr::err_str(
      CalcitErrKind::Type,
      format!("&call-dylib-edn-fn expected a lib_name, got: {}", xs[0]),
    );
  };

  let method: String = if let Calcit::Str(s) = &xs[1] {
    (**s).to_owned()
  } else {
    return CalcitErr::err_str(
      CalcitErrKind::Type,
      format!("&call-dylib-edn-fn expected a method name, got: {}", xs[1]),
    );
  };
  let mut ys: Vec<Edn> = Vec::with_capacity(xs.len() - 2);
  let callback = xs[xs.len() - 1].to_owned();
  let size = xs.len();
  for (idx, v) in xs.iter().enumerate() {
    if idx > 1 && idx < size - 1 {
      ys.push(calcit_to_edn(v)?);
    }
  }
  if let Calcit::Fn { .. } = callback {
  } else {
    return CalcitErr::err_str(
      CalcitErrKind::Type,
      format!("expected last argument to be callback fn, got: {callback}"),
    );
  }

  track::track_task_add();
  trace_ffi_event("task-add", format!("kind=callback pending={}", track::count_pending_tasks()));

  trace_ffi_event(
    "spawn-callback",
    format!(
      "lib={lib_name} resolved={} symbol={method} argc={} args={}",
      resolve_trace_path(&lib_name),
      ys.len(),
      format_edn_args_for_trace(&ys)
    ),
  );

  let lib = load_dylib(&lib_name)?;
  ensure_abi_compatible(&lib, &lib_name)?;
  let copied_stack_1 = Arc::new(call_stack.to_owned());
  let method_name = method.clone();
  let lib_name_for_thread = lib_name.clone();

  let _handle = thread::spawn(move || {
    trace_ffi_event(
      "thread-start",
      format!(
        "lib={lib_name_for_thread} symbol={method_name} pending={}",
        track::count_pending_tasks()
      ),
    );
    let callback_method_name = method_name.clone();
    let callback_lib_name = lib_name_for_thread.clone();
    trace_ffi_event("lookup-symbol", format!("lib={lib_name_for_thread} symbol={method_name}"));
    let func: libloading::Symbol<EdnFfiFn> = match unsafe { lib.get(method_name.as_bytes()) } {
      Ok(f) => f,
      Err(e) => {
        track::track_task_release();
        trace_ffi_event("task-release", format!("kind=callback pending={}", track::count_pending_tasks()));
        return CalcitErr::err_str(
          CalcitErrKind::Unexpected,
          format!("failed to load FFI symbol `{method_name}` in `{lib_name_for_thread}`: {e}"),
        );
      }
    };
    let copied_stack = copied_stack_1.to_owned();
    match func(
      ys.to_owned(),
      Arc::new(move |ps: Vec<Edn>| -> Result<Edn, String> {
        trace_ffi_event(
          "callback-in",
          format!(
            "lib={callback_lib_name} symbol={callback_method_name} argc={} args={}",
            ps.len(),
            format_edn_args_for_trace(&ps)
          ),
        );
        if let Calcit::Fn { info, .. } = &callback {
          let mut real_args: Vec<Calcit> = vec![];
          for p in ps {
            real_args.push(edn_to_calcit(&p, &Calcit::Nil));
          }
          let r = runner::run_fn(&real_args, info, &copied_stack);
          match r {
            Ok(ret) => {
              let ret_edn = calcit_to_edn(&ret)?;
              trace_ffi_event(
                "callback-out",
                format!(
                  "lib={callback_lib_name} symbol={callback_method_name} ret={}",
                  format_edn_args_for_trace(std::slice::from_ref(&ret_edn))
                ),
              );
              Ok(ret_edn)
            }
            Err(e) => {
              display_stack(&format!("[Error] thread callback failed: {}", e.msg), &e.stack, e.location.as_ref())?;
              Err(format!("Error: {e}"))
            }
          }
        } else {
          Err(format!("expected last argument to be callback fn, got: {callback}"))
        }
      }),
      Arc::new(track::track_task_release),
    ) {
      Ok(ret) => {
        trace_ffi_event(
          "return-callback",
          format!(
            "lib={lib_name_for_thread} symbol={method_name} ret={}",
            format_edn_args_for_trace(std::slice::from_ref(&ret))
          ),
        );
        edn_to_calcit(&ret, &Calcit::Nil)
      }
      Err(e) => {
        track::track_task_release();
        trace_ffi_event("task-release", format!("kind=callback pending={}", track::count_pending_tasks()));
        trace_ffi_event("error-callback", format!("lib={lib_name_for_thread} symbol={method_name} {e}"));
        // let _ = display_stack(&format!("failed to call request: {}", e), &copied_stack_1);
        eprintln!("failure inside ffi thread: {e}");
        return CalcitErr::err_str(CalcitErrKind::Unexpected, e);
      }
    };
    Ok(Calcit::Nil)
  });

  Ok(Calcit::Nil)
}

/// pass callback function to FFI function, blocking the thread,
/// used by calcit-paint, where main thread is required
pub fn blocking_dylib_edn_fn(xs: Vec<Calcit>, call_stack: &CallStackList) -> Result<Calcit, CalcitErr> {
  if xs.len() < 3 {
    return CalcitErr::err_str(
      CalcitErrKind::Arity,
      format!("&blocking-dylib-edn-fn expected >3 arguments, got: {xs:?}"),
    );
  }

  let lib_name: String = if let Calcit::Str(s) = &xs[0] {
    (**s).to_owned()
  } else {
    return CalcitErr::err_str(
      CalcitErrKind::Type,
      format!("&blocking-dylib-edn-fn expected a lib_name, got: {}", xs[0]),
    );
  };

  let method: String = if let Calcit::Str(s) = &xs[1] {
    (**s).to_owned()
  } else {
    return CalcitErr::err_str(
      CalcitErrKind::Type,
      format!("&blocking-dylib-edn-fn expected a method name, got: {}", xs[1]),
    );
  };
  let mut ys: Vec<Edn> = Vec::with_capacity(xs.len() - 2);
  let callback = xs[xs.len() - 1].to_owned();
  let size = xs.len();
  for (idx, v) in xs.iter().enumerate() {
    if idx > 1 && idx < size - 1 {
      ys.push(calcit_to_edn(v)?);
    }
  }
  if let Calcit::Fn { .. } = callback {
  } else {
    return CalcitErr::err_str(
      CalcitErrKind::Type,
      format!("expected last argument to be callback fn, got: {callback}"),
    );
  }

  track::track_task_add();
  trace_ffi_event("task-add", format!("kind=blocking pending={}", track::count_pending_tasks()));

  trace_ffi_event(
    "blocking-call",
    format!(
      "lib={lib_name} resolved={} symbol={method} argc={} args={}",
      resolve_trace_path(&lib_name),
      ys.len(),
      format_edn_args_for_trace(&ys)
    ),
  );

  let lib = unsafe { libloading::Library::new(&lib_name) }
    .map_err(|e| CalcitErr::use_str(CalcitErrKind::Unexpected, format!("failed to load dylib `{lib_name}`: {e}")))?;
  ensure_abi_compatible(&lib, &lib_name)?;
  let copied_stack = Arc::new(call_stack.to_owned());
  let callback_method = method.clone();
  let callback_lib_name = lib_name.clone();

  let func: libloading::Symbol<EdnFfiFn> = unsafe { lib.get(method.as_bytes()) }.map_err(|e| {
    CalcitErr::use_str(
      CalcitErrKind::Unexpected,
      format!("failed to load FFI symbol `{method}` in `{lib_name}`: {e}"),
    )
  })?;
  match func(
    ys.to_owned(),
    Arc::new(move |ps: Vec<Edn>| -> Result<Edn, String> {
      trace_ffi_event(
        "blocking-callback-in",
        format!(
          "lib={callback_lib_name} symbol={callback_method} argc={} args={}",
          ps.len(),
          format_edn_args_for_trace(&ps)
        ),
      );
      if let Calcit::Fn { info, .. } = &callback {
        let mut real_args: Vec<Calcit> = vec![];
        for p in ps {
          real_args.push(edn_to_calcit(&p, &Calcit::Nil));
        }
        let r = runner::run_fn(&real_args, info, &copied_stack);
        match r {
          Ok(ret) => {
            let ret_edn = calcit_to_edn(&ret)?;
            trace_ffi_event(
              "blocking-callback-out",
              format!(
                "lib={callback_lib_name} symbol={callback_method} ret={}",
                format_edn_args_for_trace(std::slice::from_ref(&ret_edn))
              ),
            );
            Ok(ret_edn)
          }
          Err(e) => {
            display_stack(&format!("[Error] thread callback failed: {}", e.msg), &e.stack, e.location.as_ref())?;
            Err(format!("Error: {e}"))
          }
        }
      } else {
        Err(format!("expected last argument to be callback fn, got: {callback}"))
      }
    }),
    Arc::new(track::track_task_release),
  ) {
    Ok(ret) => {
      trace_ffi_event(
        "blocking-return",
        format!(
          "lib={lib_name} symbol={method} ret={}",
          format_edn_args_for_trace(std::slice::from_ref(&ret))
        ),
      );
      edn_to_calcit(&ret, &Calcit::Nil)
    }
    Err(e) => {
      trace_ffi_event("blocking-error", format!("lib={lib_name} symbol={method} {e}"));
      // TODO for more accurate tracking, need to place tracker inside foreign function
      // track::track_task_release();
      let _ = display_stack(&format!("failed to call request: {e}"), call_stack, None);
      return CalcitErr::err_str(CalcitErrKind::Unexpected, e);
    }
  };

  Ok(Calcit::Nil)
}

/// need to put it here since the crate does not compile for dylib
#[unsafe(no_mangle)]
pub fn on_ctrl_c(xs: Vec<Calcit>, call_stack: &CallStackList) -> Result<Calcit, CalcitErr> {
  if xs.len() == 1 {
    let cb = Arc::new(xs[0].to_owned());
    let copied_stack = Arc::new(call_stack.to_owned());
    ctrlc::set_handler(move || {
      if let Calcit::Fn { info, .. } = cb.as_ref()
        && let Err(e) = runner::run_fn(&[], info, &copied_stack)
      {
        eprintln!("error: {e}");
      }
    })
    .map_err(|e| CalcitErr::use_str(CalcitErrKind::Unexpected, format!("failed to set Ctrl-C handler: {e}")))?;
    Ok(Calcit::Nil)
  } else {
    CalcitErr::err_str(CalcitErrKind::Arity, format!("on-control-c expected a callback function {xs:?}"))
  }
}