Commit 398b4ed8 authored by Luboš Luňák's avatar Luboš Luňák
Browse files

[clang] detect switch fallthrough marked by a comment (PR43465) 

The regex can be extended if needed, but this should probably handle
most of the cases.

Differential Revision: https://reviews.llvm.org/D73852
parent 388de9df

clang/lib/Sema/AnalysisBasedWarnings.cpp

+36 −0
Original line number Diff line number Diff line
@@ -1148,6 +1148,11 @@ namespace { 
          continue;

        }



        if (isFollowedByFallThroughComment(LastStmt)) {

          ++AnnotatedCnt;

          continue; // Fallthrough comment, good.

        }



        ++UnannotatedCnt;

      }

      return !!UnannotatedCnt;
@@ -1208,10 +1213,41 @@ namespace { 
      return nullptr;

    }



    bool isFollowedByFallThroughComment(const Stmt *Statement) {

      // Try to detect whether the fallthough is marked by a comment like

      // /*FALLTHOUGH*/.

      bool Invalid;

      const char *SourceData = S.getSourceManager().getCharacterData(

          Statement->getEndLoc(), &Invalid);

      if (Invalid)

        return false;

      const char *LineStart = SourceData;

      for (;;) {

        LineStart = strchr(LineStart, '\n');

        if (LineStart == nullptr)

          return false;

        ++LineStart; // Start of next line.

        const char *LineEnd = strchr(LineStart, '\n');

        StringRef Line(LineStart,

                       LineEnd ? LineEnd - LineStart : strlen(LineStart));

        if (LineStart == LineEnd ||

            Line.find_first_not_of(" \t\r") == StringRef::npos)

          continue; // Whitespace-only line.

        if (!FallthroughRegex.isValid())

          FallthroughRegex =

              llvm::Regex("(/\\*[ \\t]*fall(s | |-)?thr(ough|u)\\.?[ \\t]*\\*/)"

                          "|(//[ \\t]*fall(s | |-)?thr(ough|u)\\.?[ \\t]*)",

                          llvm::Regex::IgnoreCase);

        assert(FallthroughRegex.isValid());

        return FallthroughRegex.match(Line);

      }

    }



    bool FoundSwitchStatements;

    AttrStmts FallthroughStmts;

    Sema &S;

    llvm::SmallPtrSet<const CFGBlock *, 16> ReachableBlocks;

    llvm::Regex FallthroughRegex;

  };

} // anonymous namespace

clang/test/Sema/fallthrough-comment.c

0 → 100644
+20 −0
Original line number Diff line number Diff line 
// RUN: %clang_cc1 -fsyntax-only -std=c11 -verify -Wimplicit-fallthrough %s



int fallthrough_comment(int n) {

  switch (n) {

  case 0:

    n++;

    // FALLTHROUGH

  case 1:

    n++;



    /*fall-through.*/



  case 2:

    n++;

  case 3: // expected-warning{{unannotated fall-through between switch labels}} expected-note{{insert '__attribute__((fallthrough));' to silence this warning}} expected-note{{insert 'break;' to avoid fall-through}}

    n++;

    break;

  }

  return n;

}