Diagnose uninitialized uses of a variable within its own initializer.

This is basically the same idea as the warning on uninitialized uses of
fields within an initializer list. As such, it is on by default and
under -Wuninitialized.

Original patch by Richard Trieu, with some massaging from me on the
wording and grouping of the diagnostics.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@128376 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 44 insertions, 1 deletions

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 59b4f5f229..7a1492a53b 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -25,6 +25,7 @@
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/DeclTemplate.h"
+#include "clang/AST/EvaluatedExprVisitor.h"
 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/StmtCXX.h"
 #include "clang/AST/CharUnits.h"
@@ -4664,6 +4665,46 @@ bool Sema::CheckForConstantInitializer(Expr *Init, QualType DclT) {
   return true;
 }
 
+namespace {
+  // Visits an initialization expression to see if OrigDecl is evaluated in
+  // its own initialization and throws a warning if it does.
+  class SelfReferenceChecker
+      : public EvaluatedExprVisitor<SelfReferenceChecker> {
+    Sema &S;
+    Decl *OrigDecl;
+
+  public:
+    typedef EvaluatedExprVisitor<SelfReferenceChecker> Inherited;
+
+    SelfReferenceChecker(Sema &S, Decl *OrigDecl) : Inherited(S.Context),
+                                                    S(S), OrigDecl(OrigDecl) { }
+
+    void VisitExpr(Expr *E) {
+      if (isa<ObjCMessageExpr>(*E)) return;
+      Inherited::VisitExpr(E);
+    }
+
+    void VisitImplicitCastExpr(ImplicitCastExpr *E) {
+      CheckForSelfReference(E);
+      Inherited::VisitImplicitCastExpr(E);
+    }
+
+    void CheckForSelfReference(ImplicitCastExpr *E) {
+      if (E->getCastKind() != CK_LValueToRValue) return;
+      Expr* SubExpr = E->getSubExpr()->IgnoreParenImpCasts();
+      DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(SubExpr);
+      if (!DRE) return;
+      Decl* ReferenceDecl = DRE->getDecl();
+      if (OrigDecl != ReferenceDecl) return;
+      LookupResult Result(S, DRE->getNameInfo(), Sema::LookupOrdinaryName,
+                          Sema::NotForRedeclaration);
+      S.Diag(SubExpr->getLocStart(), diag::warn_uninit_self_reference_in_init)
+        << Result.getLookupName() << OrigDecl->getLocation()
+        << SubExpr->getSourceRange();
+    }
+  };
+}
+
 /// AddInitializerToDecl - Adds the initializer Init to the
 /// declaration dcl. If DirectInit is true, this is C++ direct
 /// initialization rather than copy initialization.
@@ -4674,6 +4715,8 @@ void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init,
   if (RealDecl == 0 || RealDecl->isInvalidDecl())
     return;
 
+  SelfReferenceChecker(*this, RealDecl).VisitExpr(Init);
+
   if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(RealDecl)) {
     // With declarators parsed the way they are, the parser cannot
     // distinguish between a normal initializer and a pure-specifier.
@@ -5231,7 +5274,7 @@ Sema::FinalizeDeclaratorGroup(Scope *S, const DeclSpec &DS,
     if (Decl *D = Group[i])
       Decls.push_back(D);
 
-  return BuildDeclaratorGroup(Decls.data(), Decls.size(), 
+  return BuildDeclaratorGroup(Decls.data(), Decls.size(),
                               DS.getTypeSpecType() == DeclSpec::TST_auto);
 }