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

[Nick Desaulniers via Phabricator via cfe-commits]

nickdesaulniers added a comment.

Thanks for the patch, I look forward to this feature!

I think the changes in `test/SemaCXX/warn-unused-label-error.cpp`, `test/Sema/block-literal.c`, and `test/Sema/address_spaces.c` should not be committed (2 look like unrelated cleanups?).



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Comment at: lib/Parse/ParseStmt.cpp:110-111
 
   assert((Attrs.empty() || Res.isInvalid() || Res.isUsable()) &&
          "attributes on empty statement");
 
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Wouldn't this statement have to change? `__attribute__((fallthrough))` //is// an "attribute on [an] empty statement."  Maybe this is not the correct place to try to parse a GNU attr?


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Comment at: lib/Sema/AnalysisBasedWarnings.cpp:1279
         continue;
-      if (S.getLangOpts().CPlusPlus11) {
+      if (S.getLangOpts().CPlusPlus11 || S.getLangOpts().C99) {
         const Stmt *Term = B->getTerminatorStmt();
----------------
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=`?


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Comment at: test/Sema/block-literal.c:44
   takeblock(^{ x = 4; });  // expected-error {{variable is not assignable (missing __block type specifier)}}
-  __block y = 7;    // expected-warning {{type specifier missing, defaults to 'int'}}
-  takeblock(^{ y = 8; });
+  __block y = 7;    // expected-error {{use of undeclared identifier 'y'}}
+  takeblock(^{ y = 8; }); // expected-error {{use of undeclared identifier 'y'}}
----------------
xbolva00 wrote:
> I tried look at this, but I have no idea how my change to parse GNU affects __block.
If you remove your change to `lib/Parse/ParseStmt.cpp`, does this test still fail in this way?  Did you test this on an assertion enabled build (`-DLLVM_ENABLE_ASSERTIONS=ON`)? (I would have expected the assertion I commented on above to fail.)


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Comment at: test/Sema/fallthrough-attr.c:1
+// RUN: %clang_cc1 -fsyntax-only -std=c99 -verify -Wimplicit-fallthrough %s
+// RUN: %clang_cc1 -fsyntax-only -std=c11 -verify -Wimplicit-fallthrough %s
----------------
would you mind adding a run for `-std=gnu89`? In particular, I'm worried about you're above change checking c99.


Repository:
  rC Clang

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

https://reviews.llvm.org/D63260