gsub with empty regex doesn't terminate #1206
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I can reproduce this bug with current master (0b82185). |
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Seems that empty matches also cause this bug. |
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Related issue: #2148 |
This was referenced Jun 19, 2023
pkoppstein
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Jun 29, 2023
… uniq(stream) The primary purpose of this commit (which supercedes PR jqlang#2624) is to rectify most problems with `gsub` (and also `sub` with the "g" option), in particular jqlang#1425 ('\b'), jqlang#2354 (lookahead), and jqlang#2532 (regex == "^(?!cd ).*$|^cd ";"")). This commit also partly resolves jqlang#2148 and jqlang#1206 in that `gsub` no longer loops infinitely; however, because the new `gsub` depends critically on match(_;"g"), the behavior when regex == "" is sometimes non-standard. [*1] Since the new sub/3 relies on uniq/1, that has been added as well [*2]. The documentation has been updated to reflect the fact that `sub` and `gsub` are intended to be regular in the second argument. [*3] Also, _nwise/1 has been tweaked to take advantage of TCO. Footnotes: [*1] Using the new gsub, '"a" | gsub( ""; "a")' emits "aa" rather than "aaa" as would be standard. This is nevertheless better than the infinite loop behavior of jq 1.6 in this case. With one exception (as explained in [*2]), the new gsub is implemented as though match/2 behavior is correct. That is, bugs in `gsub` behavior will most likely have their origin in `match/2`. [*2] `uniq/1` adopts the Unix/Linux name and semantics; it is needed for the following test case: gsub("(?=u)"; "u") "qux" "quux" Without this functionality: Test jqlang#23: 'gsub("(?=u)"; "u")' at line number 100 *** Expected "quux", but got "quuux" for test at line number 102: gsub("(?=u)"; "u") The root of the problem here is `match`: if `match` is fixed, then gsub would not need `untie`. The addition of `uniq` as a top-level function should be a non-issue relative to general concern about builtins.jq bloat: the line count of the new builtin.jq is significantly reduced overall, and the number of defs is actually reduced by 1 (from 111 (ignoring a redundant def) to 110). [*3] See e.g. jqlang#513 (comment)
itchyny
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Jul 3, 2023
The primary purpose of this commit is to rectify most problems with `gsub` (and also `sub` with the `g` option), in particular fix #1425 ('\b'), fix #2354 (lookahead), and fix #2532 (regex == `"^(?!cd ).*$|^cd "`). This commit also partly resolves #2148 and resolves #1206 in that `gsub` no longer loops infinitely; however, because the new `gsub` depends critically on `match/2`, the behavior when regex == `""` is sometimes non-standard. The documentation has been updated to reflect the fact that `sub` and `gsub` are intended to be regular in the second argument. Also, `_nwise/1` has been tweaked to take advantage of TCO.
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Calling
gsubwith an empty regex will run forever. Example:$ jq -n '"" | gsub(""; "")'Not sure if this is a bug or expected behavior, but terminating with an error might be more appropriate :)
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