Cabal doesn't pass *-options to GHC when compiling ordinary Haskell sources

[zlonast]

Will close issues #9801 #4435
Main idea #9801 (comment)

*-options should be always passed when invoking GHC, similarly as ghc-options should be always used when invoking ghc - regardless of what is the intention of a particular GHC-call. GHC might use or not use the options, Cabal cannot know and should not guess.

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[zlonast]

I probably need to think about tests, maybe something started working besides CApiFFI 🤔

[zlonast]

Ok, this only works for things newer than 8.8
gcc: fatal error: cannot specify ‘-o’ with ‘-c’, ‘-S’ or ‘-E’ with multiple files

Ok, got it, we just need to separate the flags -optc and -optcxx
Pass -optcxx for GHC >= 8.10 #7072

[zlonast]

@ulysses4ever @phadej It's not very easy to add flags to sources files due to backward compatibility, so for now I suggest considering the pull request as is ¯\_(ツ)_/¯ (Anyway, this solved the problem with macros in header files)

[ulysses4ever]

Great start, thank you! Below are some inline questions.

One general question: did you check that this doesn't lead to duplicated options when cabal calls GHC? I assume other *-options are passed today sometimes. So, sometimes we'll get those options passed as today and through your change too. Is that right? It seems undesirable.

It's not very easy to add flags to sources files due to backward compatibility

Can you be more specific? Do you mean it's hard to test on older GHCs? This shouldn't be a problem because the tests can run for specific versions of GHC (e.g. starting from 8.10).

[ulysses4ever]

Please, also add the issues field

[ulysses4ever]

Can you specify exactly which *-options are meant currently? (ASM, LD, etc...) And explain what's the difference with how there handled now: I assume they're passed only under specific circumstances now. Which ones?

[ulysses4ever]

But the patch does something to other *-options too. Is it possible to test this change w.r.t. other *-options?

[geekosaur]

Same concerns as @ulysses4ever raised.

[phadej]

this is wrong. You should check for the configured compiler, not the one used to compile Cabal.

[phadej]

did you check that this doesn't lead to duplicated options when cabal calls GHC?

Yes, it looks like so.

I'd say the problem is rather that GhcOptions is not used uniformly. There is e.g. componentCcGhcOptions which does set ghcOptCcOptions. Why these don't show up when compiling files CApiFFI headers?

IMHO, it's wrong that there are separate componentAsmGhcOptions, componentJsGhcOptions, componentGhcOptions. There should be just one componentGhcOptions with all the options, and then it's up to GHC which ones are relevant, and which aren't.

EDIT: There might be situations where ghcOptMode or something like that is different, and input files "obviously". But the bulk of options should be the same. Starting with verbosity. I'd imagine there is only single line in the codebase which does ghcOptVerbosity = toFlag (min verbosity normal). Currently there are six copies of that. Cannot be right. I suspect there are many subtle inconsistencies hiding because of that.

EDIT: So AFAICT, this is not the correct fix, not what I'd imagine seeing.