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Fix try/catch catches more than it should #1859 #2750

Merged
merged 1 commit into from
Jul 24, 2023
Merged

Fix try/catch catches more than it should #1859 #2750

merged 1 commit into from
Jul 24, 2023

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nicowilliams
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@nicowilliams nicowilliams commented Jul 22, 2023 •
edited by emanuele6
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Rename the FORK_OPT opcode to TRY_BEGIN, add a TRY_END opcode, and wrap errors when raising through a TRY_END so that they will not be caught by the matching TRY_BEGIN.

Now a try exp catch handler expression generates code like:

TRY_BEGIN handler
<exp>
TRY_END
JUMP past_handler
handler: <handler>
past_handler:
...

On backtrack through TRY_BEGIN it just backtracks.

If anything past the whole thing raises when produced a value, then the TRY_END will catch the error, wrap it in another, and backtrack. The TRY_BEGIN will see a wrapped error and then it will unwrap and re-raise the error.

If raises, then TRY_BEGIN will catch the error and jump to the handler, but the TRY_BEGIN will not stack_save() in that case, so on raise/backtrack the TRY_BEGIN will not execute again (nor will the TRY_END).

Resolves #1859, resolves #1885, resolves #2140, resolves #2220, resolves #2485, resolves #2073.

@nicowilliams
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This is a straight-forward cherry-pick of ee36e9a from my old dlopen branch. There were minimal conflicts. Let's see if it works (er, well, it's failing jqtest for me locally, so it needs more work).

@nicowilliams nicowilliams added this to the 1.7 release milestone Jul 22, 2023
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It does not matter much, but, probably because of the way you have ./configure-ed your build locally, in parser.c, all the #line directives have the hardcoded full path to your parser.y/parser.c files (/home/nico/ws/jq/src/parser.y) instead of just src/parser.y; and instead of the boring #ifndef YY_YY_SRC_PARSER_H_INCLUDED, it now uses #ifndef YY_YY__HOME_NICO_WS_JQ_SRC_PARSER_H_INCLUDED. =D

emanuele6
emanuele6 reviewed Jul 22, 2023
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wader
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@nicowilliams
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It does not matter much, but, probably because of the way you have ./configure-ed your build locally, in parser.c, all the #line directives have the hardcoded full path to your parser.y/parser.c files (/home/nico/ws/jq/src/parser.y) instead of just src/parser.y; and instead of the boring #ifndef YY_YY_SRC_PARSER_H_INCLUDED, it now uses #ifndef YY_YY__HOME_NICO_WS_JQ_SRC_PARSER_H_INCLUDED. =D

😆

That's pretty funny. It's probably because I used --srcdir=/home/nico/ws/jq, except using --srcdir=.. didn't help. Hmm.

@nicowilliams nicowilliams force-pushed the fix_try_catch_catches_too_much branch from 15c5fbe to 8a60d40 Compare July 23, 2023 04:41
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I think the issues above are fixed.

@nicowilliams nicowilliams force-pushed the fix_try_catch_catches_too_much branch from 8a60d40 to 6052fee Compare July 23, 2023 04:53
@nicowilliams nicowilliams marked this pull request as ready for review July 23, 2023 22:06
@itchyny
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itchyny commented Jul 23, 2023

Here's a list of issues that this PR fixes. Hope some examples from there will be included.

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itchyny commented Jul 23, 2023

Here's also an example; jq -n 'first(.?,.?)' that might have been fixed by this PR.

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nicowilliams commented Jul 23, 2023 •
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@itchyny nice finds! I'll check them out and add tests based on them.

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nicowilliams commented Jul 23, 2023 •
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Here's also an example; jq -n 'first(.?,.?)' that might have been fixed by this PR.

Oh, that's ugly, but no, this PR wouldn't fix that. This PR is strictly about try/catch, and first/1 doesn't use try/catch. and yes, this fixes it.

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nicowilliams commented Jul 24, 2023 •
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Looks like I might have cherry-picked the wrong commit. See #1885 (comment).

@nicowilliams
Fix try/catch catches more than it should jqlang#1859
db93945 
Close jqlang#1885, jqlang#2140, jqlang#2011, jqlang#2220, jqlang#2485, 2073

Rename the FORK_OPT opcode to TRY_BEGIN, add a TRY_END opcode, and wrap
errors when raising through a TRY_END so that they will not be caught by
the matching TRY_BEGIN.

Now a `try exp catch handler` expression generates code like:

    TRY_BEGIN handler
    <exp>
    TRY_END
    JUMP past_handler
    handler: <handler>
    past_handler:
    ...

On backtrack through TRY_BEGIN it just backtracks.

If anything past the whole thing raises when <exp> produced a value,
then the TRY_END will catch the error, wrap it in another, and
backtrack.  The TRY_BEGIN will see a wrapped error and then it will
unwrap and re-raise the error.

If <exp> raises, then TRY_BEGIN will catch the error and jump to the
handler, but the TRY_BEGIN will not stack_save() in that case, so on
raise/backtrack the TRY_BEGIN will not execute again (nor will the
TRY_END).
@nicowilliams nicowilliams force-pushed the fix_try_catch_catches_too_much branch from 6052fee to db93945 Compare July 24, 2023 01:30
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@itchyny I think this is ready now.