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

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 55223ac134351d3e3a2a4fd596ca960af2d84894..6e0bec2f1fe4f24d16ee34d4ed413e8b99bf2e58 100644 (file)
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -871,6 +871,9 @@ def note_uninit_reference_member : Note<
   "uninitialized reference member is here">;
 def warn_field_is_uninit : Warning<"field is uninitialized when used here">,
   InGroup<Uninitialized>;
+def warn_uninit_self_reference_in_init : Warning<
+  "variable %0 is uninitialized when used within its own initialization">,
+  InGroup<Uninitialized>;
 def warn_uninit_var : Warning<"variable %0 is possibly uninitialized when used here">,
   InGroup<Uninitialized>, DefaultIgnore;
 def warn_maybe_uninit_var :

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 59b4f5f2292f388faf1b5f42826114268fbad3a3..7a1492a53b553f8669125e1f6ed97601847db49c 100644 (file)
--- 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);
 }
 

diff --git a/test/PCH/pragma-diag-section.cpp b/test/PCH/pragma-diag-section.cpp
index 312f720ebd987ff41b6a9f0cbf5249246baafd0d..5b996bb2f0d16f438e1301b4f28c0dc6a6469ef6 100644 (file)
--- a/test/PCH/pragma-diag-section.cpp
+++ b/test/PCH/pragma-diag-section.cpp
@@ -12,7 +12,10 @@
 #pragma clang diagnostic ignored "-Wtautological-compare"
 template <typename T>
 struct TS {
-    void m() { T b = b==b; }
+    void m() {
+      T a = 0;
+      T b = a==a;
+    }
 };
 #pragma clang diagnostic pop
 

diff --git a/test/PCH/pragma-diag.c b/test/PCH/pragma-diag.c
index c5171036400f35be84f6e1a6ab83a8e02f7d7301..b304c4bf8c35fe7b12701324dcc40b7c74fddff4 100644 (file)
--- a/test/PCH/pragma-diag.c
+++ b/test/PCH/pragma-diag.c
@@ -13,7 +13,8 @@
 #else
 
 void f() {
-  int b = b==b;
+  int a = 0;
+  int b = a==a;
 }
 
 #endif

diff --git a/test/PCH/rdar8852495.c b/test/PCH/rdar8852495.c
index 2d49e001b05158c529f18b5b3eacc255ff552fef..fb465a37ce38da00f78ed52cd4f9eba4cfdac532 100644 (file)
--- a/test/PCH/rdar8852495.c
+++ b/test/PCH/rdar8852495.c
@@ -16,7 +16,8 @@
 #else
 
 int f() {
-  int b = b==b;
+  int a;
+  int b = a==a;
   unsigned x;
   signed y;
   return x == y;

diff --git a/test/Preprocessor/pragma_diagnostic_sections.cpp b/test/Preprocessor/pragma_diagnostic_sections.cpp
index 69436b0bd84e801cdb24e7a1cb7a369077dc9667..b680fae5b993ff498b8887540c0e97b98414bfd1 100644 (file)
--- a/test/Preprocessor/pragma_diagnostic_sections.cpp
+++ b/test/Preprocessor/pragma_diagnostic_sections.cpp
@@ -2,14 +2,14 @@
 
 // rdar://8365684
 struct S {
-    void m1() { int b = b==b; } // expected-warning {{always evaluates to true}}
+    void m1() { int b; while (b==b); } // expected-warning {{always evaluates to true}}
 
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wtautological-compare"
-    void m2() { int b = b==b; }
+    void m2() { int b; while (b==b); }
 #pragma clang diagnostic pop
 
-    void m3() { int b = b==b; } // expected-warning {{always evaluates to true}}
+    void m3() { int b; while (b==b); } // expected-warning {{always evaluates to true}}
 };
 
 //------------------------------------------------------------------------------
@@ -18,7 +18,7 @@ struct S {
 #pragma clang diagnostic ignored "-Wtautological-compare"
 template <typename T>
 struct TS {
-    void m() { T b = b==b; }
+    void m() { T b; while (b==b); }
 };
 #pragma clang diagnostic pop