string repeat has an infinite loop #9899
Description
[
fish --version
#=>
fish, version 3.6.1
uname -a
#=>
Linux hostname 6.4.2-1-default #1 SMP PREEMPT_DYNAMIC Mon Jul 10 10:03:25 UTC 2023 (b97b894) x86_64 x86_64 x86_64 GNU/Linux
echo $TERM
#=>
xterm-256color
(opensuse tumbleweed)
]
I just ran into this while throwing together a quick test for how another program (ag) behaves with different line lengths.
(ie, just to give context of how I stumbled on this fish thing, this otherwise unrelated issue with ag x --print-long-lines.)
I originally set up the test using line lengths of 2 20 200 2000 20000
(
$
for n in 2 20 200 2000 20000
echo (string repeat -n (math "$n-1") _)x > file_$n.txt
end)
and it worked fine...
But when I tried to bump that upper 20000 down to a mere 3000
(cuz fun github fact, apparently "There was an error creating your Issue: body is too long (maximum is 65536 characters).")
(
$
for n in 2 20 200 2000 3000
echo (string repeat -n (math "$n-1") _)x > file_$n.txt
end)
I got the error:
Too much data emitted by command substitution so it was discarded
echo (string repeat -n (math "$n-1") _)x > file_$n.txt
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
I was utterly mystified that the code worked with 20k characters,
but a mere 3k was apparently too much,
but skipping over the rest of the story of how I stumbled through isolating the problem more and more,
I ended up testing for completeness sake up to the highest number I practically could,
which was 524288
(
cuz in the following for-loop I used,
that was the highest that doesn't result in the error:
fish: Expansion produced too many results
which by contrast is an entirely straightforward and comprehensible limitation that I wouldn't even really call a "bug"...
)
So I ran this test:
$
echo -n > failures
for n in (seq 1 524288)
if echo (string repeat -n $n _)x &>/dev/null
echo OK $n
else
echo FAIL $n | tee -a failures
end
endwhich got specifically 348 numbers it fails for...
In summary, the pattern looks like (for $n, and $n+1:
$n = 2999,4499,5999,7499,8999,10499,11999,[...],514499,515999,517499,518999,520499,521999,523499
$n+1 = 3000,4500,6000,7500,9000,10500,12000,[...],514500,516000,517500,519000,520500,522000,523500
Which... looks like there's some clear and obvious pattern to it,
but damned if I'd have a clue where it comes from.
Reformatting the output a bit, the full list is:
# # actual $n in my test # $n+1
FAIL 2999 3000
FAIL 4499 4500
FAIL 5999 6000
FAIL 7499 7500
FAIL 8999 9000
FAIL 10499 10500
FAIL 11999 12000
FAIL 13499 13500
FAIL 14999 15000
FAIL 16499 16500
FAIL 17999 18000
FAIL 19499 19500
FAIL 20999 21000
FAIL 22499 22500
FAIL 23999 24000
FAIL 25499 25500
FAIL 26999 27000
FAIL 28499 28500
FAIL 29999 30000
FAIL 31499 31500
FAIL 32999 33000
FAIL 34499 34500
FAIL 35999 36000
FAIL 37499 37500
FAIL 38999 39000
FAIL 40499 40500
FAIL 41999 42000
FAIL 43499 43500
FAIL 44999 45000
FAIL 46499 46500
FAIL 47999 48000
FAIL 49499 49500
FAIL 50999 51000
FAIL 52499 52500
FAIL 53999 54000
FAIL 55499 55500
FAIL 56999 57000
FAIL 58499 58500
FAIL 59999 60000
FAIL 61499 61500
FAIL 62999 63000
FAIL 64499 64500
FAIL 65999 66000
FAIL 67499 67500
FAIL 68999 69000
FAIL 70499 70500
FAIL 71999 72000
FAIL 73499 73500
FAIL 74999 75000
FAIL 76499 76500
FAIL 77999 78000
FAIL 79499 79500
FAIL 80999 81000
FAIL 82499 82500
FAIL 83999 84000
FAIL 85499 85500
FAIL 86999 87000
FAIL 88499 88500
FAIL 89999 90000
FAIL 91499 91500
FAIL 92999 93000
FAIL 94499 94500
FAIL 95999 96000
FAIL 97499 97500
FAIL 98999 99000
FAIL 100499 100500
FAIL 101999 102000
FAIL 103499 103500
FAIL 104999 105000
FAIL 106499 106500
FAIL 107999 108000
FAIL 109499 109500
FAIL 110999 111000
FAIL 112499 112500
FAIL 113999 114000
FAIL 115499 115500
FAIL 116999 117000
FAIL 118499 118500
FAIL 119999 120000
FAIL 121499 121500
FAIL 122999 123000
FAIL 124499 124500
FAIL 125999 126000
FAIL 127499 127500
FAIL 128999 129000
FAIL 130499 130500
FAIL 131999 132000
FAIL 133499 133500
FAIL 134999 135000
FAIL 136499 136500
FAIL 137999 138000
FAIL 139499 139500
FAIL 140999 141000
FAIL 142499 142500
FAIL 143999 144000
FAIL 145499 145500
FAIL 146999 147000
FAIL 148499 148500
FAIL 149999 150000
FAIL 151499 151500
FAIL 152999 153000
FAIL 154499 154500
FAIL 155999 156000
FAIL 157499 157500
FAIL 158999 159000
FAIL 160499 160500
FAIL 161999 162000
FAIL 163499 163500
FAIL 164999 165000
FAIL 166499 166500
FAIL 167999 168000
FAIL 169499 169500
FAIL 170999 171000
FAIL 172499 172500
FAIL 173999 174000
FAIL 175499 175500
FAIL 176999 177000
FAIL 178499 178500
FAIL 179999 180000
FAIL 181499 181500
FAIL 182999 183000
FAIL 184499 184500
FAIL 185999 186000
FAIL 187499 187500
FAIL 188999 189000
FAIL 190499 190500
FAIL 191999 192000
FAIL 193499 193500
FAIL 194999 195000
FAIL 196499 196500
FAIL 197999 198000
FAIL 199499 199500
FAIL 200999 201000
FAIL 202499 202500
FAIL 203999 204000
FAIL 205499 205500
FAIL 206999 207000
FAIL 208499 208500
FAIL 209999 210000
FAIL 211499 211500
FAIL 212999 213000
FAIL 214499 214500
FAIL 215999 216000
FAIL 217499 217500
FAIL 218999 219000
FAIL 220499 220500
FAIL 221999 222000
FAIL 223499 223500
FAIL 224999 225000
FAIL 226499 226500
FAIL 227999 228000
FAIL 229499 229500
FAIL 230999 231000
FAIL 232499 232500
FAIL 233999 234000
FAIL 235499 235500
FAIL 236999 237000
FAIL 238499 238500
FAIL 239999 240000
FAIL 241499 241500
FAIL 242999 243000
FAIL 244499 244500
FAIL 245999 246000
FAIL 247499 247500
FAIL 248999 249000
FAIL 250499 250500
FAIL 251999 252000
FAIL 253499 253500
FAIL 254999 255000
FAIL 256499 256500
FAIL 257999 258000
FAIL 259499 259500
FAIL 260999
8903
261000
FAIL 262499 262500
FAIL 263999 264000
FAIL 265499 265500
FAIL 266999 267000
FAIL 268499 268500
FAIL 269999 270000
FAIL 271499 271500
FAIL 272999 273000
FAIL 274499 274500
FAIL 275999 276000
FAIL 277499 277500
FAIL 278999 279000
FAIL 280499 280500
FAIL 281999 282000
FAIL 283499 283500
FAIL 284999 285000
FAIL 286499 286500
FAIL 287999 288000
FAIL 289499 289500
FAIL 290999 291000
FAIL 292499 292500
FAIL 293999 294000
FAIL 295499 295500
FAIL 296999 297000
FAIL 298499 298500
FAIL 299999 300000
FAIL 301499 301500
FAIL 302999 303000
FAIL 304499 304500
FAIL 305999 306000
FAIL 307499 307500
FAIL 308999 309000
FAIL 310499 310500
FAIL 311999 312000
FAIL 313499 313500
FAIL 314999 315000
FAIL 316499 316500
FAIL 317999 318000
FAIL 319499 319500
FAIL 320999 321000
FAIL 322499 322500
FAIL 323999 324000
FAIL 325499 325500
FAIL 326999 327000
FAIL 328499 328500
FAIL 329999 330000
FAIL 331499 331500
FAIL 332999 333000
FAIL 334499 334500
FAIL 335999 336000
FAIL 337499 337500
FAIL 338999 339000
FAIL 340499 340500
FAIL 341999 342000
FAIL 343499 343500
FAIL 344999 345000
FAIL 346499 346500
FAIL 347999 348000
FAIL 349499 349500
FAIL 350999 351000
FAIL 352499 352500
FAIL 353999 354000
FAIL 355499 355500
FAIL 356999 357000
FAIL 358499 358500
FAIL 359999 360000
FAIL 361499 361500
FAIL 362999 363000
FAIL 364499 364500
FAIL 365999 366000
FAIL 367499 367500
FAIL 368999 369000
FAIL 370499 370500
FAIL 371999 372000
FAIL 373499 373500
FAIL 374999 375000
FAIL 376499 376500
FAIL 377999 378000
FAIL 379499 379500
FAIL 380999 381000
FAIL 382499 382500
FAIL 383999 384000
FAIL 385499 385500
FAIL 386999 387000
FAIL 388499 388500
FAIL 389999 390000
FAIL 391499 391500
FAIL 392999 393000
FAIL 394499 394500
FAIL 395999 396000
FAIL 397499 397500
FAIL 398999 399000
FAIL 400499 400500
FAIL 401999 402000
FAIL 403499 403500
FAIL 404999 405000
FAIL 406499 406500
FAIL 407999 408000
FAIL 409499 409500
FAIL 410999 411000
FAIL 412499 412500
FAIL 413999 414000
FAIL 415499 415500
FAIL 416999 417000
FAIL 418499 418500
FAIL 419999 420000
FAIL 421499 421500
FAIL 422999 423000
FAIL 424499 424500
FAIL 425999 426000
FAIL 427499 427500
FAIL 428999 429000
FAIL 430499 430500
FAIL 431999 432000
FAIL 433499 433500
FAIL 434999 435000
FAIL 436499 436500
FAIL 437999 438000
FAIL 439499 439500
FAIL 440999 441000
FAIL 442499 442500
FAIL 443999 444000
FAIL 445499 445500
FAIL 446999 447000
FAIL 448499 448500
FAIL 449999 450000
FAIL 451499 451500
FAIL 452999 453000
FAIL 454499 454500
FAIL 455999 456000
FAIL 457499 457500
FAIL 458999 459000
FAIL 460499 460500
FAIL 461999 462000
FAIL 463499 463500
FAIL 464999 465000
FAIL 466499 466500
FAIL 467999 468000
FAIL 469499 469500
FAIL 470999 471000
FAIL 472499 472500
FAIL 473999 474000
FAIL 475499 475500
FAIL 476999 477000
FAIL 478499 478500
FAIL 479999 480000
FAIL 481499 481500
FAIL 482999 483000
FAIL 484499 484500
FAIL 485999 486000
FAIL 487499 487500
FAIL 488999 489000
FAIL 490499 490500
FAIL 491999 492000
FAIL 493499 493500
FAIL 494999 495000
FAIL 496499 496500
FAIL 497999 498000
FAIL 499499 499500
FAIL 500999 501000
FAIL 502499 502500
FAIL 503999 504000
FAIL 505499 505500
FAIL 506999 507000
FAIL 508499 508500
FAIL 509999 510000
FAIL 511499 511500
FAIL 512999 513000
FAIL 514499 514500
FAIL 515999 516000
FAIL 517499 517500
FAIL 518999 519000
FAIL 520499 520500
FAIL 521999 522000
FAIL 523499 523500