Gerco Dries (Dec 05 2023 at 22:37): Gerco Dries (Dec 05 2023 at 22:37):I have a program for AoC day 5 that uses the parser library to grab its input. It works fine on the test input, but fails with "segmentation fault" when running the larger puzzle input. There doesn't seem to be any information associated with this fault. No stack trace, no better error message, nothing I can grab on to and debug.
Through some experimentation I have been able to tell that it's the input parsing causing the error, rather than anything that happens later but that's where I get stuck. Are there any known problems in either "parser" or Roc itself that could explain this behavior?
inputParser : Parser (List U8) Puzzle
inputParser =
listOfSeeds =
const \seeds -> seeds
|> skip (string "seeds:")
|> skip whitespace
|> keep listOfNumbers
almanacMap =
const
(\dstStart -> \srcStart -> \length ->
range 0 length
|> List.walk (Dict.empty {}) \dict, n -> Dict.insert dict (srcStart + n) (dstStart + n))
|> keep digits
|> skip whitespace
|> keep digits
|> skip whitespace
|> keep digits
|> skip whitespace
combineDicts = \dicts ->
dicts |> List.walk (Dict.empty {}) Dict.insertAll
almanac =
const \s2s -> \s2f -> \f2w -> \w2l -> \l2t -> \t2h -> \h2l -> {
seedToSoil: s2s,
soilToFertilizer: s2f,
fertilizerToWater: f2w,
waterToLight: w2l,
lightToTemperature: l2t,
temperatureToHumidity: t2h,
humidityToLocation: h2l,
}
|> skip (string "seed-to-soil map:")
|> skip whitespace
|> keep (map (many almanacMap) combineDicts)
|> skip (string "soil-to-fertilizer map:")
|> skip whitespace
|> keep (map (many almanacMap) combineDicts)
|> skip (string "fertilizer-to-water map:")
|> skip whitespace
|> keep (map (many almanacMap) combineDicts)
|> skip (string "water-to-light map:")
|> skip whitespace
|> keep (map (many almanacMap) combineDicts)
|> skip (string "light-to-temperature map:")
|> skip whitespace
|> keep (map (many almanacMap) combineDicts)
|> skip (string "temperature-to-humidity map:")
|> skip whitespace
|> keep (map (many almanacMap) combineDicts)
|> skip (string "humidity-to-location map:")
|> skip whitespace
|> keep (map (many almanacMap) combineDicts)
const \se -> \al -> { seeds: se, almanac: al }
|> keep listOfSeeds
|> keep almanac
whitespace : Parser (List U8) _
whitespace =
const \a -> a
|> skip (many (oneOf [codeunit ' ', codeunit '\t', codeunit '\n']))
listOfNumbers : Parser (List U8) (List Nat)
listOfNumbers =
const \r -> r
|> skip whitespace
|> keep (sepBy digits whitespace)
|> skip whitespace
No issues that I am aware of, this is a compiler bug. I would put my money on List.walk with a Dict
Gerco Dries (Dec 05 2023 at 22:49):I suspect it may have something to do with being out of memory. In the code, I'm expanding dozens of ranges that turn out to be tens millions of elements long in the full test input and I don't have that much memory in my computer. The code compiles and runs just fine with a smaller input.
Luke Boswell (Dec 05 2023 at 22:57):Wouldnt that be a stack overflow though?
Luke Boswell (Dec 05 2023 at 22:57):I dont know
Brendan Hansknecht (Dec 05 2023 at 23:08):my guess. it is out of memory, but instead it returns a bad pionter which roc reads that leads to a segfault...but really need to open it with a debugger
Gerco Dries (Dec 05 2023 at 23:11):Updating the code to not expand the ranges anymore did solve the problem, so I'm thinking out of memory was the correct conclusion.
Notification Bot (Dec 06 2023 at 00:34):Gerco Dries has marked this topic as resolved.
Last updated: Jul 26 2025 at 12:14 UTC