AnalysisBasedWarnings.cpp

  //     time.
  DiagnosticsEngine &Diags = S.getDiagnostics();

  // Do not do any analysis for declarations in system headers if we are
  // going to just ignore them.
  if (Diags.getSuppressSystemWarnings() &&
      S.SourceMgr.isInSystemHeader(D->getLocation()))
    return;

  // For code in dependent contexts, we'll do this at instantiation time.
  if (cast<DeclContext>(D)->isDependentContext())
    return;

  if (Diags.hasErrorOccurred() || Diags.hasFatalErrorOccurred()) {
    // Flush out any possibly unreachable diagnostics.
    flushDiagnostics(S, fscope);
    return;
  }
  
  const Stmt *Body = D->getBody();
  assert(Body);

  AnalysisDeclContext AC(/* AnalysisDeclContextManager */ 0, D);

  // Don't generate EH edges for CallExprs as we'd like to avoid the n^2
  // explosion for destrutors that can result and the compile time hit.
  AC.getCFGBuildOptions().PruneTriviallyFalseEdges = true;
  AC.getCFGBuildOptions().AddEHEdges = false;
  AC.getCFGBuildOptions().AddInitializers = true;
  AC.getCFGBuildOptions().AddImplicitDtors = true;
  
  // Force that certain expressions appear as CFGElements in the CFG.  This
  // is used to speed up various analyses.
  // FIXME: This isn't the right factoring.  This is here for initial
  // prototyping, but we need a way for analyses to say what expressions they
  // expect to always be CFGElements and then fill in the BuildOptions
  // appropriately.  This is essentially a layering violation.
  if (P.enableCheckUnreachable || P.enableThreadSafetyAnalysis) {
    // Unreachable code analysis and thread safety require a linearized CFG.
    AC.getCFGBuildOptions().setAllAlwaysAdd();
  }
  else {
    AC.getCFGBuildOptions()
      .setAlwaysAdd(Stmt::BinaryOperatorClass)
      .setAlwaysAdd(Stmt::BlockExprClass)
      .setAlwaysAdd(Stmt::CStyleCastExprClass)
      .setAlwaysAdd(Stmt::DeclRefExprClass)
      .setAlwaysAdd(Stmt::ImplicitCastExprClass)
      .setAlwaysAdd(Stmt::UnaryOperatorClass)
      .setAlwaysAdd(Stmt::AttributedStmtClass);
  }

  // Construct the analysis context with the specified CFG build options.
  
  // Emit delayed diagnostics.
  if (!fscope->PossiblyUnreachableDiags.empty()) {
    bool analyzed = false;

    // Register the expressions with the CFGBuilder.
    for (SmallVectorImpl<sema::PossiblyUnreachableDiag>::iterator
         i = fscope->PossiblyUnreachableDiags.begin(),
         e = fscope->PossiblyUnreachableDiags.end();
         i != e; ++i) {
      if (const Stmt *stmt = i->stmt)
        AC.registerForcedBlockExpression(stmt);
    }

    if (AC.getCFG()) {
      analyzed = true;
      for (SmallVectorImpl<sema::PossiblyUnreachableDiag>::iterator
            i = fscope->PossiblyUnreachableDiags.begin(),
            e = fscope->PossiblyUnreachableDiags.end();
            i != e; ++i)
      {
        const sema::PossiblyUnreachableDiag &D = *i;
        bool processed = false;
        if (const Stmt *stmt = i->stmt) {
          const CFGBlock *block = AC.getBlockForRegisteredExpression(stmt);
          CFGReverseBlockReachabilityAnalysis *cra =
              AC.getCFGReachablityAnalysis();
          // FIXME: We should be able to assert that block is non-null, but
          // the CFG analysis can skip potentially-evaluated expressions in
          // edge cases; see test/Sema/vla-2.c.
          if (block && cra) {
            // Can this block be reached from the entrance?
            if (cra->isReachable(&AC.getCFG()->getEntry(), block))
              S.Diag(D.Loc, D.PD);
            processed = true;
          }
        }
        if (!processed) {
          // Emit the warning anyway if we cannot map to a basic block.
          S.Diag(D.Loc, D.PD);
        }
      }
    }

    if (!analyzed)
      flushDiagnostics(S, fscope);
  }
  
  
  // Warning: check missing 'return'
  if (P.enableCheckFallThrough) {
    const CheckFallThroughDiagnostics &CD =
      (isa<BlockDecl>(D) ? CheckFallThroughDiagnostics::MakeForBlock()
       : (isa<CXXMethodDecl>(D) &&
          cast<CXXMethodDecl>(D)->getOverloadedOperator() == OO_Call &&
          cast<CXXMethodDecl>(D)->getParent()->isLambda())
            ? CheckFallThroughDiagnostics::MakeForLambda()
            : CheckFallThroughDiagnostics::MakeForFunction(D));
    CheckFallThroughForBody(S, D, Body, blkExpr, CD, AC);
  }

  // Warning: check for unreachable code
  if (P.enableCheckUnreachable) {
    // Only check for unreachable code on non-template instantiations.
    // Different template instantiations can effectively change the control-flow
    // and it is very difficult to prove that a snippet of code in a template
    // is unreachable for all instantiations.
    bool isTemplateInstantiation = false;
    if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(D))
      isTemplateInstantiation = Function->isTemplateInstantiation();
    if (!isTemplateInstantiation)
      CheckUnreachable(S, AC);
  }

  // Check for thread safety violations
  if (P.enableThreadSafetyAnalysis) {
    SourceLocation FL = AC.getDecl()->getLocation();
    SourceLocation FEL = AC.getDecl()->getLocEnd();
    thread_safety::ThreadSafetyReporter Reporter(S, FL, FEL);
    thread_safety::runThreadSafetyAnalysis(AC, Reporter);
    Reporter.emitDiagnostics();
  }

  if (Diags.getDiagnosticLevel(diag::warn_uninit_var, D->getLocStart())
      != DiagnosticsEngine::Ignored ||
      Diags.getDiagnosticLevel(diag::warn_maybe_uninit_var, D->getLocStart())
      != DiagnosticsEngine::Ignored) {
    if (CFG *cfg = AC.getCFG()) {
      UninitValsDiagReporter reporter(S);
      UninitVariablesAnalysisStats stats;
      std::memset(&stats, 0, sizeof(UninitVariablesAnalysisStats));
      runUninitializedVariablesAnalysis(*cast<DeclContext>(D), *cfg, AC,
                                        reporter, stats);

      if (S.CollectStats && stats.NumVariablesAnalyzed > 0) {
        ++NumUninitAnalysisFunctions;
        NumUninitAnalysisVariables += stats.NumVariablesAnalyzed;
        NumUninitAnalysisBlockVisits += stats.NumBlockVisits;
        MaxUninitAnalysisVariablesPerFunction =
            std::max(MaxUninitAnalysisVariablesPerFunction,
                     stats.NumVariablesAnalyzed);
        MaxUninitAnalysisBlockVisitsPerFunction =
            std::max(MaxUninitAnalysisBlockVisitsPerFunction,
                     stats.NumBlockVisits);
      }
    }
  }

  if (Diags.getDiagnosticLevel(diag::warn_unannotated_fallthrough,
                              D->getLocStart()) != DiagnosticsEngine::Ignored) {
    DiagnoseSwitchLabelsFallthrough(S, AC);
  }

  // Collect statistics about the CFG if it was built.
  if (S.CollectStats && AC.isCFGBuilt()) {
    ++NumFunctionsAnalyzed;
    if (CFG *cfg = AC.getCFG()) {
      // If we successfully built a CFG for this context, record some more
      // detail information about it.
      NumCFGBlocks += cfg->getNumBlockIDs();
      MaxCFGBlocksPerFunction = std::max(MaxCFGBlocksPerFunction,
                                         cfg->getNumBlockIDs());
    } else {
      ++NumFunctionsWithBadCFGs;
    }
  }
}

void clang::sema::AnalysisBasedWarnings::PrintStats() const {
  llvm::errs() << "\n*** Analysis Based Warnings Stats:\n";

  unsigned NumCFGsBuilt = NumFunctionsAnalyzed - NumFunctionsWithBadCFGs;
  unsigned AvgCFGBlocksPerFunction =
      !NumCFGsBuilt ? 0 : NumCFGBlocks/NumCFGsBuilt;
  llvm::errs() << NumFunctionsAnalyzed << " functions analyzed ("
               << NumFunctionsWithBadCFGs << " w/o CFGs).\n"
               << "  " << NumCFGBlocks << " CFG blocks built.\n"
               << "  " << AvgCFGBlocksPerFunction
               << " average CFG blocks per function.\n"
               << "  " << MaxCFGBlocksPerFunction
               << " max CFG blocks per function.\n";

  unsigned AvgUninitVariablesPerFunction = !NumUninitAnalysisFunctions ? 0
      : NumUninitAnalysisVariables/NumUninitAnalysisFunctions;
  unsigned AvgUninitBlockVisitsPerFunction = !NumUninitAnalysisFunctions ? 0
      : NumUninitAnalysisBlockVisits/NumUninitAnalysisFunctions;
  llvm::errs() << NumUninitAnalysisFunctions
               << " functions analyzed for uninitialiazed variables\n"
               << "  " << NumUninitAnalysisVariables << " variables analyzed.\n"
               << "  " << AvgUninitVariablesPerFunction
               << " average variables per function.\n"
               << "  " << MaxUninitAnalysisVariablesPerFunction
               << " max variables per function.\n"
               << "  " << NumUninitAnalysisBlockVisits << " block visits.\n"
               << "  " << AvgUninitBlockVisitsPerFunction
               << " average block visits per function.\n"
               << "  " << MaxUninitAnalysisBlockVisitsPerFunction
               << " max block visits per function.\n";
}