[PATCH] D158301: Add back overriding-t-options for -m<os>-version-min diagnostic

[Fangrui Song via Phabricator via cfe-commits]

MaskRay added inline comments.


================
Comment at: clang/test/Driver/darwin-version.c:217
 // RUN:   FileCheck --check-prefix=CHECK-VERSION-TNO-OSV1 %s
-// CHECK-VERSION-TNO-OSV1: overriding '-mmacos-version-min=10.6' option with '-target x86_64-apple-macos10.11.2'
+// CHECK-VERSION-TNO-OSV1: overriding '-mmacos-version-min=10.6' option with '-target x86_64-apple-macos10.11.2' [-Woverriding-t-option]
 
----------------
dexonsmith wrote:
> MaskRay wrote:
> > hans wrote:
> > > MaskRay wrote:
> > > > hans wrote:
> > > > > dexonsmith wrote:
> > > > > > MaskRay wrote:
> > > > > > > dexonsmith wrote:
> > > > > > > > Why would we want to use the old name here? An alias seems strictly better to me. 
> > > > > > > Making `overriding-t-option` an alias for `overriding-option` would make `-Wno-overriding-t-option` applies to future overriding option diagnostics, which is exactly what I want to avoid.
> > > > > > > 
> > > > > > I understand that you don't want `-t-` to apply to work on future overriding option diagnostics, but I think the platform divergence you're adding here is worse.
> > > > > > 
> > > > > > Having a few Darwin-specific options use `-Woverriding-t-option` (and everything else use `-Woverriding-option`) as the canonical spelling is hard to reason about for maintainers, and for users.
> > > > > > 
> > > > > > And might not users on other platforms have `-Woverriding-t-option` hardcoded in  build settings? (So @dblaikie's argument that we shouldn't arbitrarily make things hard for users would apply to all options?)
> > > > > > 
> > > > > > IMO, if we're not comfortable removing `-Woverriding-t-option` entirely, then it should live on as an alias (easy to reason about), not as canonical-in-special-cases (hard to reason about).
> > > > > > IMO, if we're not comfortable removing -Woverriding-t-option entirely, then it should live on as an alias (easy to reason about), not as canonical-in-special-cases (hard to reason about).
> > > > > 
> > > > > +1 if we can't drop the old spelling, an alias seems like the best option.
> > > > Making `overriding-t-option` an alias for `overriding-option`, as I mentioned, will make `-Wno-overriding-t-option` affect new overriding-options uses. This is exactly what I want to avoid.
> > > > 
> > > > I know there are some `-Wno-overriding-t-option` uses. Honestly, they are far fewer than other diagnostics we are introducing or changing in Clang. I can understand the argument "make -Werror users easier for this specific diagnostic" (but `-Werror` will complain about other new diagnostics), but do we really want to in the Darwin case? I think no. They can remove the version from the target triple like https://github.com/facebook/ocamlrep/blame/abc14b8aafcc6746ec37bf7bf0de24bfc58d63a0/prelude/apple/apple_target_sdk_version.bzl#L50　or make the version part consistent with `-m.*os-version-min`.
> > > > 
> > > > This change may force these users to re-think how they should fix  their build. I apology to these users, but I don't feel that adding an alias is really necessary.
> > > > Making overriding-t-option an alias for overriding-option, as I mentioned, will make -Wno-overriding-t-option affect new overriding-options uses. This is exactly what I want to avoid.
> > > 
> > > Is keeping them separate actually important, though? -Wno-overriding-option has the same issue in that case, that using the flag will also affect any new overriding-options uses, and I don't think that's a problem.
> > `-Wno-overriding-option` is properly named, so affecting new overriding-options uses looks fine to me.
> > `-Wno-overriding-t-option` is awkward, and making it affect new uses makes me nervous.
> > 
> > The gist of my previous comment is whether the uses cases really justify a tiny bit of tech bit in clang and I think the answer is no.
> > 
> > This change is not about changing a semantic warning that has mixed opinions, e.g. `-Wbitwise-op-parentheses` (many consider it not justified).
> > The gist of my previous comment is whether the uses cases really justify a tiny bit of tech bit in clang and I think the answer is no.
> > 
> 
> I think we agree that we should add the minimal technical debt to clang.
> 
> This patch is harder-to-reason about, and thus bigger IMO, technical debt than adding an alias would be.
Honestly when people asked whether we need back compatibility for `-Werror` uses. I disagree with the idea after considering the number of uses and legitimate uses. I've well summarized them up-thread.

Making overriding-option a super set of overriding-t-option is IMHO the only solution to make -Wno-overriding-t-option not affect other uses, which is what I strive to achieve.

If `-Woverriding-t-option` looks strange for the Darwin diagnostic and we really want to work around such `-Werror` users (I disagree as I mentioned), we could rename it to something like `-Woverriding-darwin-option` or something else, and add `-Woverriding-t-option` as an alias. Then the diagnostic becomes:

> overriding '-mmacos-version-min=10.6' option with '-target x86_64-apple-macos10.11.2' [-Woverriding-darwin-option]

This would still achieve my goal of not making `overriding-t-option` affect `overriding-option`.

My most honest thinking is that we don't need any of the `overriding-t-option` tech debt. The users need to migrate. It's some work and I apologize to these users, but I don't think these uses are anything close to reasonable that justifies any debt on the clang side.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D158301/new/

https://reviews.llvm.org/D158301