[PATCH] D95691: Implement P2173 for attributes on lambdas

[John McCall via Phabricator via cfe-commits]

rjmccall added inline comments.


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Comment at: clang/include/clang/Basic/DiagnosticGroups.td:269
+def CXXPre2BCompatPedantic :
+  DiagGroup<"c++98-c++11-c++14-c++17-c++20-compat-pedantic", [CXXPre2BCompat]>;
 
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Quuxplusone wrote:
> aaron.ballman wrote:
> > rjmccall wrote:
> > > Uh, I think we're a couple standard releases past the point at which we should have reconsidered this schema.  I guess the problem is that we can't say `-Wpre-c++23-compat` without jumping the gun.  Is there a problem with `-Wc++20-compat` and then having the earlier warning groups imply the later ones?  That seems to be what we do with `-Wc++98-compat`; did we abandon that approach intentionally?
> > @rsmith may have more background here. I was following the pattern already in the file, but I tend to agree that this pattern is not leading us somewhere good. FWIW, I ran into a similar situation with this on the C side of things in D95396, so we should probably be consistent there too.
> My understanding is that the //command-line user// is expected to pass
> - `clang++ -std=c++20 -Wc++11-compat` to indicate "I want //actually// to compile in C++20 mode, but give me warnings about anything that would prevent compiling in C++11 mode"
> - `clang++ -std=c++17 -Wc++14-compat` to indicate "I want //actually// to compile in C++17 mode, but give me warnings about anything that would prevent compiling in C++14 mode"
> - `clang++ -std=c++14 -Wc++20-compat` to indicate "I want //actually// to compile in C++14 mode, but give me warnings about anything that would prevent compiling in C++20 mode" — EXCEPT that I think this is not supported. My impression is that forward-compatibility warnings are generally just rolled into `-Wall` and not handled separately beyond that?
> 
> I don't think any human user is expected to pass `-Wc++98-c++11-c++14-c++17-c++20-compat` by hand; it's just an internal name for a particular subset of `-Wc++98-compat`.
> 
> IOW, we could choose a new naming scheme for it, but that would be a purely internal change that won't affect how command-line users interact with Clang at all (for better and for worse).
Diagnostic groups can both directly contain diagnostics and imply other diagnostic groups, so I don't think there's any reason to make a dedicated group just to contain the new diagnostics in e.g. `-Wc++14-compat` except to allow someone turn on those warnings separately.  And it does show up to users as the warning group under `-fdiagnostics-show-option` (which is the default).


Repository:
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  https://reviews.llvm.org/D95691/new/

https://reviews.llvm.org/D95691