about summary refs log tree commit diff stats
path: root/apps/crenshaw2-1.subx
blob: f52c9b64ecbf2e558d765f947916f920da4c1b3b (plain) (blame)
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
# Port of https://github.com/akkartik/crenshaw/blob/master/tutor2.1.pas
# which corresponds to the section "single digits" in https://compilers.iecc.com/crenshaw/tutor2.txt
# except that we support hex digits.
#
# To run:
#   $ ./bootstrap translate init.linux [01]*.subx apps/crenshaw2-1.subx -o apps/crenshaw2-1
#   $ echo '3'  |./bootstrap run apps/crenshaw2-1
# Expected output:
#   # syscall(exit, 3)
#   bb/copy-to-ebx  3/imm32
#   b8/copy-to-eax  1/imm32/exit
#   cd/syscall  0x80/imm8
#
# To run the generated output:
#   $ echo '3'  |./bootstrap run apps/crenshaw2-1 > z1.subx
#   $ ./bootstrap translate init.linux z1.subx -o z1
#   $ ./bootstrap run z1
#   $ echo $?
#   3
#
# Stdin must contain just a single hex digit. Other input will print an error:
#   $ echo 'xyz'  |./bootstrap run apps/crenshaw2-1
#   Error: integer expected
#
# Names in this file sometimes follow Crenshaw's original rather than my usual
# naming conventions.

== code
#   instruction                     effective address                                                   register    displacement    immediate
# . op          subop               mod             rm32          base        index         scale       r32
# . 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes

Entry:  # run tests if necessary, call 'compile' if not
    # . prologue
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp

    # initialize heap
    # . Heap = new-segment(Heap-size)
    # . . push args
    68/push  Heap/imm32
    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Heap-size/disp32                  # push *Heap-size
    # . . call
    e8/call  new-segment/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp

    # - if argc > 1 and argv[1] == "test", then return run_tests()
    # if (argc <= 1) goto run-main
    81          7/subop/compare     1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0/disp8         1/imm32           # compare *ebp
    7e/jump-if-<=  $run-main/disp8
    # if (!kernel-string-equal?(argv[1], "test")) goto run-main
    # . eax = kernel-string-equal?(argv[1], "test")
    # . . push args
    68/push  "test"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
    # . . call
    e8/call  kernel-string-equal?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # . if (eax == false) goto run-main
    3d/compare-eax-and  0/imm32/false
    74/jump-if-=  $run-main/disp8
    # run-tests()
    e8/call  run-tests/disp32
    # syscall(exit, *Num-test-failures)
    8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           3/r32/ebx   Num-test-failures/disp32          # copy *Num-test-failures to ebx
    eb/jump  $main:end/disp8
$run-main:
    # - otherwise read a program from stdin and emit its translation to stdout
    # . compile(Stdin, 1/stdout, 2/stderr, ed)
    # . . push args
    68/push  0/imm32/exit-descriptor
    68/push  2/imm32/stderr
    68/push  1/imm32/stdout
    68/push  Stdin/imm32
    # . . call
    e8/call  compile/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
    # syscall(exit, 0)
    bb/copy-to-ebx  0/imm32
$main:end:
    e8/call  syscall_exit/disp32

# the main entry point
compile:  # in: (addr buffered-file), out: fd or (addr stream byte), err: fd or (addr stream byte), ed: (addr exit-descriptor)
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . save registers
    50/push-eax
    51/push-ecx
    # prime the pump
    # . Look = get-char(in)
    # . . push args
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8      .                    # push *(ebp+8)
    # . . call
    e8/call  get-char/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # var num/ecx: (stream byte 7)
    # Numbers can be 32 bits or 8 hex bytes long. One of them will be in 'Look', so we need space for 7 bytes.
    # Sizing the stream just right buys us overflow-handling for free inside 'get-num'.
    # Add 12 bytes for 'read', 'write' and 'size' fields, for a total of 19 bytes, or 0x13 in hex.
    # The stack pointer is no longer aligned, so dump_stack() can be misleading past this point.
    81          5/subop/subtract    3/mod/direct    4/rm32/esp    .           .             .           .           .               0x13/imm32        # subtract from esp
    89/copy                         3/mod/direct    1/rm32/ecx    .           .             .           4/r32/esp   .               .                 # copy esp to ecx
    # initialize the stream
    # . num->size = 7
    c7          0/subop/copy        1/mod/*+disp8   1/rm32/ecx    .           .             .           .           8/disp8         7/imm32           # copy to *(ecx+8)
    # . clear-stream(num)
    # . . push args
    51/push-ecx
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # read a digit from 'in' into 'num'
    # . get-num(in, num, err, ed)
    # . . push args
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x14/disp8      .                 # push *(ebp+20)
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x10/disp8      .                 # push *(ebp+16)
    51/push-ecx/num
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8      .                    # push *(ebp+8)
    # . . call
    e8/call  get-num/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
    # render 'num' into the following template on 'out':
    #   bb/copy-to-ebx  _num_
    #   b8/copy-to-eax  1/imm32/exit
    #   cd/syscall  0x80/imm8
    #
    # . write(out, "bb/copy-to-ebx  ")
    # . . push args
    68/push  "bb/copy-to-ebx  "/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    # . . call
    e8/call  write/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # . write-stream(out, num)
    # . . push args
    51/push-ecx/num
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    # . . call
    e8/call  write-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # . write(out, Newline)
    # . . push args
    68/push  Newline/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    # . . call
    e8/call  write/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # . write(out, "b8/copy-to-eax  1/imm32/exit\n")
    # . . push args
    68/push  "b8/copy-to-eax  1/imm32/exit\n"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    # . . call
    e8/call  write/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # . write(out, "cd/syscall  0x80/imm8\n")
    # . . push args
    68/push  "cd/syscall  0x80/imm8\n"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    # . . call
    e8/call  write/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
$compile:end:
    # . restore registers
    59/pop-to-ecx
    58/pop-to-eax
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

# Read a single digit into 'out'. Abort if there are none, or if there is no
# space in 'out'.
# Input comes from the global variable 'Look' (first byte) and the argument
# 'in' (rest). We leave the next byte from 'in' into 'Look' on exit.
get-num:  # in: (addr buffered-file), out: (addr stream byte), err: fd or (addr stream byte), ed: (addr exit-descriptor)
    # pseudocode:
    #   if (!is-digit?(Look)) expected(ed, err, "integer")
    #   if out->write >= out->size
    #     write(err, "Error: too many digits in number\n")
    #     stop(ed, 1)
    #   out->data[out->write] = LSB(Look)
    #   ++out->write
    #   Look = get-char(in)
    #
    # registers:
    #   in: esi
    #   out: edi
    #   out->write: ecx (cached copy; need to keep in sync)
    #   out->size: edx
    #   temporaries: eax, ebx
    # We can't allocate Look to a register because it gets written implicitly in
    # get-char in each iteration of the loop. (Thereby demonstrating that it's
    # not the right interface for us. But we'll keep it just to follow Crenshaw.)
    #
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # - if (is-digit?(Look)) expected(ed, err, "integer")
    # . eax = is-digit?(Look)
    # . . push args
    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Look/disp32     .                 # push *Look
    # . . call
    e8/call  is-digit?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # . if (eax == false)
    3d/compare-eax-and  0/imm32/false
    75/jump-if-!=  $get-num:main/disp8
    # . expected(ed, err, "integer")
    # . . push args
    68/push  "integer"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x10/disp8      .                 # push *(ebp+16)
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x14/disp8      .                 # push *(ebp+20)
    # . . call
    e8/call  expected/disp32  # never returns
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
$get-num:main:
    # - otherwise read a digit
    # . save registers
    50/push-eax
    51/push-ecx
    52/push-edx
    53/push-ebx
    56/push-esi
    57/push-edi
    # read necessary variables to registers
    # esi = in
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           6/r32/esi   8/disp8         .                 # copy *(ebp+8) to esi
    # edi = out
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           7/r32/edi   0xc/disp8       .                 # copy *(ebp+12) to edi
    # ecx = out->write
    8b/copy                         0/mod/indirect  7/rm32/edi    .           .             .           1/r32/ecx   .               .                 # copy *edi to ecx
    # edx = out->size
    8b/copy                         1/mod/*+disp8   7/rm32/edi    .           .             .           2/r32/edx   8/disp8         .                 # copy *(edi+8) to edx
$get-num:loop:
    # if (out->write >= out->size) error
    39/compare                      3/mod/direct    2/rm32/edx    .           .             .           1/r32/ecx   .               .                 # compare edx with ecx
    7d/jump-if-<  $get-num:stage2/disp8
    # . error(ed, err, msg)  # TODO: show full number
    # . . push args
    68/push  "get-num: too many digits in number"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x10/disp8      .                 # push *(ebp+16)
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x14/disp8      .                 # push *(ebp+20)
    # . . call
    e8/call  error/disp32  # never returns
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
$get-num:stage2:
    # out->data[out->write] = LSB(Look)
    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    7/base/edi  1/index/ecx   .           3/r32/ebx   0xc/disp8       .                 # copy edi+ecx+12 to ebx
    8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Look/disp32     .                 # copy *Look to eax
    88/copy-byte                    0/mod/indirect  3/rm32/ebx    .           .             .           0/r32/AL    .               .                 # copy byte at AL to *ebx
    # ++out->write
    41/increment-ecx
    # Look = get-char(in)
    # . . push args
    56/push-esi
    # . . call
    e8/call  get-char/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
$get-num:loop-end:
    # persist necessary variables from registers
    89/copy                         0/mod/indirect  7/rm32/edi    .           .             .           1/r32/ecx   .               .                 # copy ecx to *edi
$get-num:end:
    # . restore registers
    5f/pop-to-edi
    5e/pop-to-esi
    5b/pop-to-ebx
    5a/pop-to-edx
    59/pop-to-ecx
    58/pop-to-eax
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

test-get-num-reads-single-digit:
    # - check that get-num returns first character if it's a digit
    # This test uses exit-descriptors. Use ebp for setting up local variables.
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # clear all streams
    # . clear-stream(_test-stream)
    # . . push args
    68/push  _test-stream/imm32
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # . clear-stream($_test-buffered-file->buffer)
    # . . push args
    68/push  $_test-buffered-file->buffer/imm32
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # . clear-stream(_test-output-stream)
    # . . push args
    68/push  _test-output-stream/imm32
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # . clear-stream(_test-error-stream)
    # . . push args
    68/push  _test-error-stream/imm32
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # initialize 'in'
    # . write(_test-stream, "3")
    # . . push args
    68/push  "3"/imm32
    68/push  _test-stream/imm32
    # . . call
    e8/call  write/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # initialize exit-descriptor 'ed' for the call to 'get-num' below
    # . var ed/eax: exit-descriptor
    81          5/subop/subtract    3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # subtract from esp
    89/copy                         3/mod/direct    0/rm32/eax    .           .             .           4/r32/esp   .               .                 # copy esp to eax
    # . tailor-exit-descriptor(ed, 16)
    # . . push args
    68/push  0x10/imm32/nbytes-of-args-for-get-num
    50/push-eax/ed
    # . . call
    e8/call  tailor-exit-descriptor/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # prime the pump
    # . get-char(_test-buffered-file)
    # . . push args
    68/push  _test-buffered-file/imm32
    # . . call
    e8/call  get-char/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # get-num(in, out, err, ed)
    # . . push args
    50/push-eax/ed
    68/push  _test-error-stream/imm32
    68/push  _test-output-stream/imm32
    68/push  _test-buffered-file/imm32
    # . . call
    e8/call  get-num/disp32
    # registers except esp may be clobbered at this point
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
    # check-ints-equal(*_test-output-stream->data, '3', msg)
    # . . push args
    68/push  "F - test-get-num-reads-single-digit"/imm32
    68/push  0x33/imm32
    b8/copy-to-eax  _test-output-stream/imm32
    ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           0xc/disp8       .                 # push *(eax+12)
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # . reclaim locals
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    5d/pop-to-ebp
    c3/return

test-get-num-aborts-on-non-digit-in-Look:
    # - check that get-num returns first character if it's a digit
    # This test uses exit-descriptors. Use ebp for setting up local variables.
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # clear all streams
    # . clear-stream(_test-stream)
    # . . push args
    68/push  _test-stream/imm32
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # . clear-stream($_test-buffered-file->buffer)
    # . . push args
    68/push  $_test-buffered-file->buffer/imm32
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # . clear-stream(_test-output-stream)
    # . . push args
    68/push  _test-output-stream/imm32
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # . clear-stream(_test-error-stream)
    # . . push args
    68/push  _test-error-stream/imm32
    # . . call
    e8/call  clear-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # initialize 'in'
    # . write(_test-stream, "3")
    # . . push args
    68/push  "3"/imm32
    68/push  _test-stream/imm32
    # . . call
    e8/call  write/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # initialize exit-descriptor 'ed' for the call to 'get-num' below
    # . var ed/eax: exit-descriptor
    81          5/subop/subtract    3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # subtract from esp
    89/copy                         3/mod/direct    0/rm32/eax    .           .             .           4/r32/esp   .               .                 # copy esp to eax
    # . tailor-exit-descriptor(ed, 16)
    # . . push args
    68/push  0x10/imm32/nbytes-of-args-for-get-num
    50/push-eax/ed
    # . . call
    e8/call  tailor-exit-descriptor/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # *don't* prime the pump
    # get-num(in, out, err, ed)
    # . . push args
    50/push-eax/ed
    68/push  _test-error-stream/imm32
    68/push  _test-output-stream/imm32
    68/push  _test-buffered-file/imm32
    # . . call
    e8/call  get-num/disp32
    # registers except esp may be clobbered at this point
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
    # check that get-num tried to call exit(1)
    # . check-ints-equal(ed->value, 2, msg)  # i.e. stop was called with value 1
    # . . push args
    68/push  "F - test-get-num-aborts-on-non-digit-in-Look"/imm32
    68/push  2/imm32
    # . . push ed->value
    ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           4/disp8         .                 # push *(eax+4)
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # . reclaim locals
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    5d/pop-to-ebp
    c3/return

## helpers

# write(f, "Error: "+s+" expected\n") then stop(ed, 1)
expected:  # ed: (addr exit-descriptor), f: fd or (addr stream byte), s: (addr array byte)
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # write(f, "Error: ")
    # . . push args
    68/push  "Error: "/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    # . . call
    e8/call  write/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # write(f, s)
    # . . push args
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x10/disp8      .                 # push *(ebp+16)
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    # . . call
    e8/call  write/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # write(f, " expected\n")
    # . . push args
    68/push  " expected\n"/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    # . . call
    e8/call  write/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # stop(ed, 1)
    # . . push args
    68/push  1/imm32
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
    # . . call
    e8/call  stop/disp32
    # should never get past this point
$expected:dead-end:
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

# read a byte from 'f', and save it in 'Look'
get-char:  # f: (addr buffered-file)
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . save registers
    50/push-eax
    # eax = read-byte-buffered(f)
    # . . push args
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
    # . . call
    e8/call  read-byte-buffered/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # save eax to Look
    89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Look/disp32     .                 # copy eax to *Look
$get-char:end:
    # . restore registers
    58/pop-to-eax
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

is-digit?:  # c: int -> eax: boolean
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # eax = false
    b8/copy-to-eax  0/imm32
    # if (c < '0') return false
    81          7/subop/compare     1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         0x30/imm32        # compare *(ebp+8)
    7c/jump-if-<  $is-digit?:end/disp8
    # if (c > '9') return false
    81          7/subop/compare     1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         0x39/imm32        # compare *(ebp+8)
    7f/jump-if->  $is-digit?:end/disp8
    # otherwise return true
    b8/copy-to-eax  1/imm32
$is-digit?:end:
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

== data

Look:  # (char with some extra padding)
    0/imm32

# . . vim:nowrap:textwidth=0