[PATCH] D63260: [Attr] Support _attribute__ ((fallthrough))

[John McCall via Phabricator via cfe-commits]

rjmccall added inline comments.


================
Comment at: lib/Sema/AnalysisBasedWarnings.cpp:1279
         continue;
-      if (S.getLangOpts().CPlusPlus11) {
+      if (S.getLangOpts().CPlusPlus11 || S.getLangOpts().C99) {
         const Stmt *Term = B->getTerminatorStmt();
----------------
aaron.ballman wrote:
> xbolva00 wrote:
> > nickdesaulniers wrote:
> > > xbolva00 wrote:
> > > > nickdesaulniers wrote:
> > > > > Probably should additionally/instead check `S.getLangOpts().GNUMode` (since these are GNU C style attributes)?  I guess we want these attributes to be supported in C regardless of `-std=`?
> > > > Good point.
> > > IIUC, we allow GNU C attributes for C regardless of ISO vs GNU C.  What we want to express is "if c++11 and newer, or c".
> > > 
> > > I think this might be better expressed as:
> > > 
> > > ```
> > > if (S.getLangOpts().CPlusPlus11 || (!S.getLangOpts().CPlusPlus && !S.getLangOpts().ObjC) {
> > > ```
> > > 
> > > But maybe there's a more canonical way to express "if the language is C." (If not, maybe we can consider such a change to `LangOpt` to make this easier, but as part of this commit).
> > Yeah, I wanted to check if lang is C but I didnt find a nice way :(
> I think we want to support this attribute in ObjC because that language is based on C. In fact, I think we are supporting this attribute in all language modes regardless of -std level because the user can always use `__attribute__((fallthrough))` as a spelling.
As of a few weeks ago, you can provide custom code in a `LangOpt`; see how `ObjCNonFragileRuntime` is defined.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D63260/new/

https://reviews.llvm.org/D63260