[scan-build] fix dead store warnings emitted on Clang Sema code base

[apelete]

Summary

This fixes dead store warnings of the type "dead assignment" reported
by Clang Static Analyzer on the following files:

• lib/Sema/SemaDeclCXX.cpp,
• lib/Sema/SemaExpr.cpp,
• lib/Sema/SemaTemplate.cpp.

Signed-off-by: Apelete Seketeli <[e-mail]>

[rtrieu]

lib/Sema/SemaExpr.cpp

9694–9696

Add comment that these variables are only updated when processing MemberExpr's in the while loop.

9701–9702

Remove these lines.

9705

Add "IsDereference = NextIsDereference;" before this line.

[apelete]

[scan-build] fix dead store warnings emitted on clang code base

Changes since last revision:

• lib/Sema/SemaLookup.cpp: remove changes since they were already applied upstream,
• lib/Sema/SemaExpr.cpp: move 'IsDereference' and 'NextIsDereference' variables into the code block where they are used.

lib/Sema/SemaDeclCXX.cpp

if (TemplateParams->size() > 0) {
                                 /*ModulePrivateLoc=*/SourceLocation(),
                                 FriendLoc, TempParamLists.size() - 1,
                                 TempParamLists.data()).get();
     } else {
       // The "template<>" header is extraneous.
       Diag(TemplateParams->getTemplateLoc(), diag::err_template_tag_noparams)
         << TypeWithKeyword::getTagTypeKindName(Kind) << Name;
       isExplicitSpecialization = true;
+      (void) isExplicitSpecialization;
     }
   }
 
   if (Invalid) return nullptr;
 
   bool isAllExplicitSpecializations = true;
   for (unsigned I = TempParamLists.size(); I-- > 0; ) {
     if (TempParamLists[I]->size()) {

lib/Sema/SemaExpr.cpp

static void DiagnoseConstAssignment(Sema &S, const Expr *E,
 
   SourceRange ExprRange = E->getSourceRange();
 
   // Only emit one error on the first const found.  All other consts will emit
   // a note to the error.
   bool DiagnosticEmitted = false;
 
   // Track if the current expression is the result of a derefence, and if the
   // next checked expression is the result of a derefence.
+  // These variables are only updated when processing MemberExpr
+  // chains in the loop below.
   bool IsDereference = false;
   bool NextIsDereference = false;
 
   // Loop to process MemberExpr chains.
   while (true) {
-    IsDereference = NextIsDereference;
-    NextIsDereference = false;
-
     E = E->IgnoreParenImpCasts();
     if (const MemberExpr *ME = dyn_cast<MemberExpr>(E)) {
+      IsDereference = NextIsDereference;
       NextIsDereference = ME->isArrow();
       const ValueDecl *VD = ME->getMemberDecl();
       if (const FieldDecl *Field = dyn_cast<FieldDecl>(VD)) {
         // Mutable fields can be modified even if the class is const.
         if (Field->isMutable()) {
           assert(DiagnosticEmitted && "Expected diagnostic not emitted.");
           break;
         }
 

lib/Sema/SemaTemplate.cpp

if (TemplateParams && TemplateParams->size() > 0) {
     }
   } else if (TemplateParams) {
     if (TUK == TUK_Friend)
       Diag(KWLoc, diag::err_template_spec_friend)
         << FixItHint::CreateRemoval(
                                 SourceRange(TemplateParams->getTemplateLoc(),
                                             TemplateParams->getRAngleLoc()))
         << SourceRange(LAngleLoc, RAngleLoc);
-    else
-      isExplicitSpecialization = true;
   } else {
     assert(TUK == TUK_Friend && "should have a 'template<>' for this decl");
   }
 
   // Check that the specialization uses the same tag kind as the
   // original template.
   TagTypeKind Kind = TypeWithKeyword::getTagTypeKindForTypeSpec(TagSpec);
   assert(Kind != TTK_Enum && "Invalid enum tag in class template spec!");