Allow CaseStmt to be initialized with a SubStmt

[xazax.hun]

Summary

The CaseStmt constructor now takes an optional SubStmt argument to initialize its SubExprs field with. This fixes an issue where the ASTImporter was constructing a CaseStmt and not setting its SubStmt member, causing a null pointer access when the SubStmt is accessed in the Stmt::stripLabelLikeStatements() function.

[khazem]

(added more context)

[ABataev]

Add a test

include/clang/AST/Stmt.h

697

I don't think you need this new param. You can create an instance if CaseStmt, then call setSubStmt() and after that return this instance.

[xazax.hun]

Since r316069 this is no longer relevant.

include/clang/AST/Stmt.h

 
 class CaseStmt : public SwitchCase {
   SourceLocation EllipsisLoc;
   enum { LHS, RHS, SUBSTMT, END_EXPR };
   Stmt* SubExprs[END_EXPR];  // The expression for the RHS is Non-null for
                              // GNU "case 1 ... 4" extension
 public:
   CaseStmt(Expr *lhs, Expr *rhs, SourceLocation caseLoc,
-           SourceLocation ellipsisLoc, SourceLocation colonLoc)
+           SourceLocation ellipsisLoc, SourceLocation colonLoc,
+           Stmt *SubStmt=nullptr)
     : SwitchCase(CaseStmtClass, caseLoc, colonLoc) {
-    SubExprs[SUBSTMT] = nullptr;
+    SubExprs[SUBSTMT] = SubStmt;
     SubExprs[LHS] = reinterpret_cast<Stmt*>(lhs);
     SubExprs[RHS] = reinterpret_cast<Stmt*>(rhs);
     EllipsisLoc = ellipsisLoc;
   }
 
   /// \brief Build an empty switch case statement.
   explicit CaseStmt(EmptyShell Empty) : SwitchCase(CaseStmtClass, Empty) { }
 

lib/AST/ASTImporter.cpp

 
 Stmt *ASTNodeImporter::VisitCaseStmt(CaseStmt *S) {
   Expr *ToLHS = Importer.Import(S->getLHS());
   if (!ToLHS)
     return nullptr;
   Expr *ToRHS = Importer.Import(S->getRHS());
   if (!ToRHS && S->getRHS())
     return nullptr;
+  Stmt *SubStmt = Importer.Import(S->getSubStmt());
+  if (!SubStmt && S->getSubStmt())
+    return nullptr;
   SourceLocation ToCaseLoc = Importer.Import(S->getCaseLoc());
   SourceLocation ToEllipsisLoc = Importer.Import(S->getEllipsisLoc());
   SourceLocation ToColonLoc = Importer.Import(S->getColonLoc());
-  return new (Importer.getToContext()) CaseStmt(ToLHS, ToRHS,
-                                                ToCaseLoc, ToEllipsisLoc,
-                                                ToColonLoc);
+  return new (Importer.getToContext()) CaseStmt(ToLHS, ToRHS, ToCaseLoc,
+                                                ToEllipsisLoc, ToColonLoc,
+                                                SubStmt);
 }
 
 Stmt *ASTNodeImporter::VisitDefaultStmt(DefaultStmt *S) {
   SourceLocation ToDefaultLoc = Importer.Import(S->getDefaultLoc());
   SourceLocation ToColonLoc = Importer.Import(S->getColonLoc());
   Stmt *ToSubStmt = Importer.Import(S->getSubStmt());
   if (!ToSubStmt && S->getSubStmt())
     return nullptr;