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Use response files for ghc invocations #9367

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@Gabriella439 Gabriella439 commented Oct 24, 2023

Before this change, cabal could fail with the following error message when building very large Haskell packages:

ghc: createProcess: posix_spawnp: resource exhausted (Argument list too long)

This is because when the number of modules or dependencies grows large enough, then the ghc command line can potentially exceed the ARG_MAX command line length limit.

However, ghc supports response files in order to work around these sorts of command line length limitations, so this change enables the use of those response files.

Note that this requires taking a special precaution to not pass RTS options to the response file because there's no way that ghc can support RTS options via the response file. The reason why is because the Haskell runtime processes these options (not ghc), so if you store the RTS options in the response file then ghc's command line parser won't know what to do with them.

This means that ghc commands can still potentially fail if the RTS options get long enough, but this is less likely to occur in practice since RTS options tend to be significantly smaller than non-RTS options.

This also requires skipping the response file if the first argument is --interactive. See the corresponding code comment which explains why in more detail.

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Depends-on: #10292

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Note that this has been tested internally at Mercury not just for cabal commands but also downstream tools (like ghcid and haskell-language-server), which is how we stumbled upon the hie-bios issue.

We ran into this issue when building our internal Haskell monolith (which has ~7000 Haskell modules), and we verified that this change fixes the problem without breaking anything else.

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Can you run fourmolu on this (make style)? That check is failing.

Cabal/src/Distribution/Simple/Program/GHC.hs Outdated Show resolved Hide resolved
@Gabriella439 Gabriella439 force-pushed the gabriella/response_files_2 branch 2 times, most recently from bbe0bd2 to b689455 Compare October 24, 2023 23:10
Cabal/src/Distribution/Simple/Program/GHC.hs Outdated Show resolved Hide resolved
Cabal/src/Distribution/Simple/Program/GHC.hs Outdated Show resolved Hide resolved
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Thanks a lot @Gabriella439 for this contribution. 🙇

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Gabriella439 commented Oct 27, 2023

I'm trying to reproduce the problem locally, but when I run ./validate.sh -s build && ./validate.sh -s lib-suite I get a whole bunch of tests being skipped with "SKIP no cabal-install" and I'm not sure how to fix that

where
(newIsRTSOption, newResponseFileArgs, newOtherArgs) =
case arg of
"+RTS" -> (True, responseFileArgs, arg : otherArgs)
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I wonder if this function already exists in cabal (something similar already exists as filterRtsOpts), perhaps abstract that and call the same function in both places?


withResponseFile
verbosity
defaultTempFileOptions
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Can you please add an option to keep this temporary file, in fact, is it a bug that cabal repl supports --keep-temp-files but that option is not honoured here?

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Looks like a good direction of travel to me.

I want to block this being merged until there is a way to keep the response file around.

A very common workflow for me is to copy the command line which cabal invokes GHC with so that I can debug GHC issues without going through cabal, it seems this patch would regress that workflow.

9999years added a commit to MercuryTechnologies/cabal that referenced this pull request Aug 29, 2024
Currently, `cabal repl` has a `--keep-temp-files` option, and
`cabal.project` has a `keep-temp-files` option but it only effects
Haddock builds.

This patch adds `--keep-temp-files` to `CommonSetupFlags`, making it
available to all commands. The expanded `--keep-temp-files` flag is used
for the `cabal repl` command and Haddock builds (retaining compatibility
with the previous behavior). The flag will also be used for response
files; see haskell#9367.
@9999years 9999years force-pushed the gabriella/response_files_2 branch 6 times, most recently from eff868d to 6d2f9f3 Compare September 3, 2024 19:09
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The requested support for preserving the temp files ended up being much more complicated to implement than I thought it would be, and I just wanted to check with the maintainers to make sure I'm on the right track.

I've put the flag in SetupCommonOptions because those are already passed to the build functions that need them, and I've attempted to thread it through the conversion functions in D.C.ProjectConfig.Legacy, but I keep getting test failures from the value getting dropped somewhere in the round-trip conversion; this is with cabal test cabal-install:unit-tests --test-options="-p ProjectConfig":

projectConfigKeepTempFiles = -NoFlag +Flag False,

Am I missing something? Is there a simpler way of doing this?

@9999years 9999years force-pushed the gabriella/response_files_2 branch 7 times, most recently from e170a59 to 7d04b62 Compare September 5, 2024 16:36
@9999years 9999years force-pushed the gabriella/response_files_2 branch 2 times, most recently from 07570f9 to 25d97f8 Compare September 6, 2024 19:57
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Ready for review, but we should probably merge #10292 first for the --keep-temp-files changes.

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Added a dependency so Mergify will hold off until it's merged.

Before this change, `cabal` could fail with the following error message
when building very large Haskell packages:

```
ghc: createProcess: posix_spawnp: resource exhausted (Argument list too long)
```

This is because when the number of modules or dependencies grows large
enough, then the `ghc` command line can potentially exceed the
`ARG_MAX` command line length limit.

However, `ghc` supports response files in order to work around these
sorts of command line length limitations, so this change enables the
use of those response files.

Note that this requires taking a special precaution to not pass RTS
options to the response file because there's no way that `ghc` can
support RTS options via the response file.  The reason why is because
the Haskell runtime processes these options (not `ghc`), so if you
store the RTS options in the response file then `ghc`'s command line
parser won't know what to do with them.

This means that `ghc` commands can still potentially fail if the RTS
options get long enough, but this is less likely to occur in practice
since RTS options tend to be significantly smaller than non-RTS
options.

This also requires skipping the response file if the first argument
is `--interactive`.  See the corresponding code comment which explains
why in more detail.

Co-Authored-By: Gabriella Gonzales <[email protected]>
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Ready for review! #10292 is merged and I've added a release note.

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6 participants