[PATCH] D94169: [clang][driver] Restore the original help text for `-I`

[Andrzej Warzynski via Phabricator via cfe-commits]

awarzynski added a comment.

In D94169#2484968 <https://reviews.llvm.org/D94169#2484968>, @andreil99 wrote:

> I'm fine with having this text in the ClangCommandLineReference.rst only, and removing it from `clang -help`.
>
> However, reverting the patch would not do, as ClangCommandLineReference.rst is auto-generated from `clang/include/clang/Driver/Options.td`. Please feel free to propose a patch for this.
>
> The rationale for the change was multiple requests from our users, since this is important for them and is what they have to discover by experiments.

Thank you for providing the context, that's much appreciated. As the original patch already contained changes in `ClangCommandLineReference.rst `, I assumed that it was completely separate from `Options.td`. My bad for not double-checking.

To the best of my knowledge, there is no mechanism to tweak the help message for an option (i.e. what's specified in `Options.td` cannot be tweaked elsewhere). So the only alternative for Flang would be to introduce a completely new option to represent `-I`, e.g.:

  def I_for_Flang JoinedOrSeparate<["-"], "I">, Group<I_Group>, Flags<[FC1Option, FlangOption]>, MetaVarName<"<dir>">,
      HelpText<"Add directory to include search path>;

However, as Flang and Clang are meant to share `libclangDriver` [1], and `Options.td ` is part of `libclangDriver`, I feel that these drivers should also share as many option definitions as possible. To me `OPT_I` is a good example of an option that should be shared.

I'm keen to resolve this in a way that's satisfactory for everyone. Personally I feel that adding `def I_for_Flang` would be detrimental to `libclangDriver`. Bearing in mind that the original change was introduced without a review, I would appreciate if more people could chime in.  Any thoughts @richard.barton.arm ?

[1] https://lists.llvm.org/pipermail/cfe-dev/2020-July/066393.html


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