Add a warning for implicit conversion from function literals (and static

methods) to bool. E.g.

void foo() {}
if (f) { ... // <- Warns here.
}

Only applies to non-weak functions, and does not apply if the function address
is taken explicitly with the addr-of operator.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@145849 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index fa2fabcdeb8841be23cb01c215d62fd745697729..9a5a664d69c9bcbce406733e85051c51f11c70b3 100644 (file)
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1650,6 +1650,9 @@ def warn_impcast_bool_to_null_pointer : Warning<
 def warn_impcast_null_pointer_to_integer : Warning<
     "implicit conversion of NULL constant to integer">,
     InGroup<DiagGroup<"conversion">>, DefaultIgnore;
+def warn_impcast_function_to_bool : Warning<
+    "address of function %q0 will always evaluate to 'true'">,
+    InGroup<BoolConversions>;
 
 def warn_cast_align : Warning<
   "cast from %0 to %1 increases required alignment from %2 to %3">,

diff --git a/lib/Sema/SemaChecking.cpp b/lib/Sema/SemaChecking.cpp
index 0d640a8c123cafa9bce5bc983aa86233a78d998e..1ec7e39398b64a489fdf4e76abc6c930fc392f92 100644 (file)
--- a/lib/Sema/SemaChecking.cpp
+++ b/lib/Sema/SemaChecking.cpp
@@ -3758,6 +3758,25 @@ void CheckImplicitConversion(Sema &S, Expr *E, QualType T,
       // by a check in AnalyzeImplicitConversions().
       return DiagnoseImpCast(S, E, T, CC,
                              diag::warn_impcast_string_literal_to_bool);
+    if (Source->isFunctionType()) {
+      // Warn on function to bool. Checks free functions and static member
+      // functions. Weakly imported functions are excluded from the check,
+      // since it's common to test their value to check whether the linker
+      // found a definition for them.
+      ValueDecl *D = 0;
+      if (DeclRefExpr* R = dyn_cast<DeclRefExpr>(E)) {
+        D = R->getDecl();
+      } else if (MemberExpr *M = dyn_cast<MemberExpr>(E)) {
+        D = M->getMemberDecl();
+      }
+
+      if (D && !D->isWeak()) {
+        FunctionDecl* F = cast<FunctionDecl>(D);
+        S.Diag(E->getExprLoc(), diag::warn_impcast_function_to_bool)
+          << F << E->getSourceRange() << SourceRange(CC);
+        return;
+      }
+    }
     return; // Other casts to bool are not checked.
   }
 

diff --git a/test/CXX/over/over.over/p2-resolve-single-template-id.cpp b/test/CXX/over/over.over/p2-resolve-single-template-id.cpp
index 1bd0d340748ba143586471161a146f17e79b0497..470894990076a3895d8a20009ef2cf51e5801029 100644 (file)
--- a/test/CXX/over/over.over/p2-resolve-single-template-id.cpp
+++ b/test/CXX/over/over.over/p2-resolve-single-template-id.cpp
@@ -100,8 +100,8 @@ int main()
   { (void) reinterpret_cast<int>(two); } //expected-error {{reinterpret_cast}}
   { (void) reinterpret_cast<int (*)(char, double)>(two); } //expected-error {{reinterpret_cast}}
 
-  { bool b = (twoT<int>); } // ok
-  { bool b = (twoT<int, int>); } //ok
+  { bool b = (twoT<int>); } // expected-warning {{address of function 'twoT<int>' will always evaluate to 'true'}}
+  { bool b = (twoT<int, int>); } // expected-warning {{address of function 'twoT<int, int>' will always evaluate to 'true'}}
 
   { bool b = &twoT<int>; //&foo<int>; }
     b = &(twoT<int>); }
@@ -142,20 +142,20 @@ namespace member_pointers {
     if (&s.f<char>) return; // expected-error {{cannot create a non-constant pointer to member function}}
     if (&s.f<int>) return; // expected-error {{cannot create a non-constant pointer to member function}}
 
-    if (S::g<char>) return;
-    if (S::g<int>) return;
+    if (S::g<char>) return; // expected-warning {{address of function 'member_pointers::S::g<char>' will always evaluate to 'true'}}
+    if (S::g<int>) return; // expected-warning {{address of function 'member_pointers::S::g<int>' will always evaluate to 'true'}}
     if (&S::g<char>) return;
     if (&S::g<int>) return;
-    if (s.g<char>) return;
-    if (s.g<int>) return;
+    if (s.g<char>) return; // expected-warning {{address of function 'member_pointers::S::g<char>' will always evaluate to 'true'}}
+    if (s.g<int>) return; // expected-warning {{address of function 'member_pointers::S::g<int>' will always evaluate to 'true'}}
     if (&s.g<char>) return;
     if (&s.g<int>) return;
 
-    if (S::h<42>) return;
+    if (S::h<42>) return; // expected-warning {{address of function 'member_pointers::S::h<42>' will always evaluate to 'true'}}
     if (S::h<int>) return; // expected-error {{reference to overloaded function could not be resolved; did you mean to call it?}}
     if (&S::h<42>) return;
     if (&S::h<int>) return;
-    if (s.h<42>) return;
+    if (s.h<42>) return;  // expected-warning {{address of function 'member_pointers::S::h<42>' will always evaluate to 'true'}}
     if (s.h<int>) return; // expected-error {{reference to overloaded function could not be resolved; did you mean to call it?}}
     if (&s.h<42>) return;
     if (&s.h<int>) return; // expected-error {{reference to overloaded function could not be resolved; did you mean to call it?}}
@@ -170,20 +170,20 @@ namespace member_pointers {
     { bool b = &s.f<char>; } // expected-error {{cannot create a non-constant pointer to member function}}
     { bool b = &s.f<int>; } // expected-error {{cannot create a non-constant pointer to member function}}
 
-    { bool b = S::g<char>; }
-    { bool b = S::g<int>; }
+    { bool b = S::g<char>; } // expected-warning {{address of function 'member_pointers::S::g<char>' will always evaluate to 'true'}}
+    { bool b = S::g<int>; } // expected-warning {{address of function 'member_pointers::S::g<int>' will always evaluate to 'true'}}
     { bool b = &S::g<char>; }
     { bool b = &S::g<int>; }
-    { bool b = s.g<char>; }
-    { bool b = s.g<int>; }
+    { bool b = s.g<char>; }  // expected-warning {{address of function 'member_pointers::S::g<char>' will always evaluate to 'true'}}
+    { bool b = s.g<int>; } // expected-warning {{address of function 'member_pointers::S::g<int>' will always evaluate to 'true'}}
     { bool b = &s.g<char>; }
     { bool b = &s.g<int>; }
 
-    { bool b = S::h<42>; }
+    { bool b = S::h<42>; } // expected-warning {{address of function 'member_pointers::S::h<42>' will always evaluate to 'true'}}
     { bool b = S::h<int>; } // expected-error {{can't form member pointer of type 'bool' without '&' and class name}}
     { bool b = &S::h<42>; }
     { bool b = &S::h<int>; }
-    { bool b = s.h<42>; }
+    { bool b = s.h<42>; }  // expected-warning {{address of function 'member_pointers::S::h<42>' will always evaluate to 'true'}}
     { bool b = s.h<int>; } // expected-error {{can't form member pointer of type 'bool' without '&' and class name}}
     { bool b = &s.h<42>; }
     { bool b = &s.h<int>; } // expected-error {{can't form member pointer of type 'bool' without '&' and class name}}

diff --git a/test/SemaCXX/condition.cpp b/test/SemaCXX/condition.cpp
index 3441bae67076b9d317ecfd6c0bd28a074bd74cad..21671fab3c04728c8feb21f59c1907eeb5638bb4 100644 (file)
--- a/test/SemaCXX/condition.cpp
+++ b/test/SemaCXX/condition.cpp
@@ -49,6 +49,6 @@ void test3() {
   if ("help")
     (void) 0;
 
-  if (test3)
+  if (test3) // expected-warning {{address of function 'test3' will always evaluate to 'true'}}
     (void) 0;
 }

diff --git a/test/SemaTemplate/resolve-single-template-id.cpp b/test/SemaTemplate/resolve-single-template-id.cpp
index b9833d8609ef316e18927b4a4cd94807db05798a..1beb65a0f510d71fd5e97a2b347383b7c6f10701 100644 (file)
--- a/test/SemaTemplate/resolve-single-template-id.cpp
+++ b/test/SemaTemplate/resolve-single-template-id.cpp
@@ -41,7 +41,7 @@ int main()
   *oneT<int>;   // expected-warning {{expression result unused}}
   *two;  //expected-error {{reference to overloaded function could not be resolved; did you mean to call it with no arguments?}} expected-error {{indirection requires pointer operand}}
   *twoT<int>; //expected-error {{reference to overloaded function could not be resolved; did you mean to call it?}}
-  !oneT<int>;  // expected-warning {{expression result unused}}
+  !oneT<int>;  // expected-warning {{expression result unused}} expected-warning {{address of function 'oneT<int>' will always evaluate to 'true'}}
   +oneT<int>;  // expected-warning {{expression result unused}}
   -oneT<int>;  //expected-error {{invalid argument type}}
   oneT<int> == 0;   // expected-warning {{equality comparison result unused}} \
@@ -53,7 +53,7 @@ int main()
   
   int i = (int) (false ? (void (*)(int))twoT<int> : oneT<int>); //expected-error {{incompatible operand}}
   (twoT<int>) == oneT<int>; //expected-error {{reference to overloaded function could not be resolved; did you mean to call it?}} {{cannot resolve overloaded function 'twoT' from context}}
-  bool b = oneT<int>;
+  bool b = oneT<int>; // expected-warning {{address of function 'oneT<int>' will always evaluate to 'true'}}
   void (*p)() = oneT<int>;
   test<oneT<int> > ti;
   void (*u)(int) = oneT<int>;