[cfe-commits] r161501 - in /cfe/trunk: include/clang/AST/Expr.h include/clang/Basic/DiagnosticGroups.td include/clang/Basic/DiagnosticSemaKinds.td lib/AST/Expr.cpp lib/Sema/SemaExpr.cpp lib/Sema/SemaOverload.cpp test/SemaCXX/constant-expression-c
Nico Weber
thakis at chromium.org
Fri Aug 17 15:33:36 PDT 2012
Should this really be on by default? On chrome, this triggers a single
time (linux-only):
../../third_party/tcmalloc/chromium/src/stack_trace_table.cc:138:16:
warning: expression which evaluates to zero treated as a null pointer
constant of type 'void *' [-Wnon-literal-null-conversion]
out[idx++] = static_cast<uintptr_t>(0);
^~~~~~~~~~~~~~~~~~~~~~~~~
out is declared as `void** out = new void*[out_len];`. The warning
isn't wrong, but it looks rather pedantic to me. Should this be only
in -Wall (or maybe even in -pedantic)?
On Wed, Aug 8, 2012 at 10:33 AM, David Blaikie <dblaikie at gmail.com> wrote:
> Author: dblaikie
> Date: Wed Aug 8 12:33:31 2012
> New Revision: 161501
>
> URL: http://llvm.org/viewvc/llvm-project?rev=161501&view=rev
> Log:
> Implement warning for integral null pointer constants other than the literal 0.
>
> This is effectively a warning for code that violates core issue 903 & thus will
> become standard error in the future, hopefully. It catches strange null
> pointers such as: '\0', 1 - 1, const int null = 0; etc...
>
> There's currently a flaw in this warning (& the warning for 'false' as a null
> pointer literal as well) where it doesn't trigger on comparisons (ptr == '\0'
> for example). Fix to come in a future patch.
>
> Also, due to this only being a warning, not an error, it triggers quite
> frequently on gtest code which tests expressions for null-pointer-ness in a
> SFINAE context (so it wouldn't be a problem if this was an error as in an
> actual implementation of core issue 903). To workaround this for now, the
> diagnostic does not fire in unevaluated contexts.
>
> Review by Sean Silva and Richard Smith.
>
> Modified:
> cfe/trunk/include/clang/AST/Expr.h
> cfe/trunk/include/clang/Basic/DiagnosticGroups.td
> cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
> cfe/trunk/lib/AST/Expr.cpp
> cfe/trunk/lib/Sema/SemaExpr.cpp
> cfe/trunk/lib/Sema/SemaOverload.cpp
> cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp
> cfe/trunk/test/SemaCXX/lambda-expressions.cpp
> cfe/trunk/test/SemaTemplate/explicit-instantiation.cpp
> cfe/trunk/test/SemaTemplate/instantiate-member-class.cpp
>
> Modified: cfe/trunk/include/clang/AST/Expr.h
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/Expr.h?rev=161501&r1=161500&r2=161501&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/AST/Expr.h (original)
> +++ cfe/trunk/include/clang/AST/Expr.h Wed Aug 8 12:33:31 2012
> @@ -541,8 +541,15 @@
> /// \brief Expression is not a Null pointer constant.
> NPCK_NotNull = 0,
>
> - /// \brief Expression is a Null pointer constant built from a zero integer.
> - NPCK_ZeroInteger,
> + /// \brief Expression is a Null pointer constant built from a zero integer
> + /// expression that is not a simple, possibly parenthesized, zero literal.
> + /// C++ Core Issue 903 will classify these expressions as "not pointers"
> + /// once it is adopted.
> + /// http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#903
> + NPCK_ZeroExpression,
> +
> + /// \brief Expression is a Null pointer constant built from a literal zero.
> + NPCK_ZeroLiteral,
>
> /// \brief Expression is a C++0X nullptr.
> NPCK_CXX0X_nullptr,
>
> Modified: cfe/trunk/include/clang/Basic/DiagnosticGroups.td
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticGroups.td?rev=161501&r1=161500&r2=161501&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/DiagnosticGroups.td (original)
> +++ cfe/trunk/include/clang/Basic/DiagnosticGroups.td Wed Aug 8 12:33:31 2012
> @@ -33,6 +33,7 @@
> def SignConversion : DiagGroup<"sign-conversion">;
> def BoolConversion : DiagGroup<"bool-conversion">;
> def IntConversion : DiagGroup<"int-conversion">;
> +def NonLiteralNullConversion : DiagGroup<"non-literal-null-conversion">;
> def NullConversion : DiagGroup<"null-conversion">;
> def BuiltinRequiresHeader : DiagGroup<"builtin-requires-header">;
> def CXXCompat: DiagGroup<"c++-compat">;
> @@ -314,7 +315,8 @@
> StringConversion,
> SignConversion,
> BoolConversion,
> - NullConversion,
> + NullConversion, // NULL->non-pointer
> + NonLiteralNullConversion, // (1-1)->pointer (etc)
> IntConversion]>,
> DiagCategory<"Value Conversion Issue">;
>
>
> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=161501&r1=161500&r2=161501&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Wed Aug 8 12:33:31 2012
> @@ -1896,6 +1896,9 @@
> def warn_impcast_bool_to_null_pointer : Warning<
> "initialization of pointer of type %0 to null from a constant boolean "
> "expression">, InGroup<BoolConversion>;
> +def warn_non_literal_null_pointer : Warning<
> + "expression which evaluates to zero treated as a null pointer constant of "
> + "type %0">, InGroup<NonLiteralNullConversion>;
> def warn_impcast_null_pointer_to_integer : Warning<
> "implicit conversion of NULL constant to %0">,
> InGroup<NullConversion>;
>
> Modified: cfe/trunk/lib/AST/Expr.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Expr.cpp?rev=161501&r1=161500&r2=161501&view=diff
> ==============================================================================
> --- cfe/trunk/lib/AST/Expr.cpp (original)
> +++ cfe/trunk/lib/AST/Expr.cpp Wed Aug 8 12:33:31 2012
> @@ -2903,7 +2903,7 @@
> llvm_unreachable("Unexpected value dependent expression!");
> case NPC_ValueDependentIsNull:
> if (isTypeDependent() || getType()->isIntegralType(Ctx))
> - return NPCK_ZeroInteger;
> + return NPCK_ZeroExpression;
> else
> return NPCK_NotNull;
>
> @@ -2977,7 +2977,12 @@
> return NPCK_NotNull;
> }
>
> - return (EvaluateKnownConstInt(Ctx) == 0) ? NPCK_ZeroInteger : NPCK_NotNull;
> + if (EvaluateKnownConstInt(Ctx) != 0)
> + return NPCK_NotNull;
> +
> + if (isa<IntegerLiteral>(this))
> + return NPCK_ZeroLiteral;
> + return NPCK_ZeroExpression;
> }
>
> /// \brief If this expression is an l-value for an Objective C
>
> Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=161501&r1=161500&r2=161501&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaExpr.cpp Wed Aug 8 12:33:31 2012
> @@ -4632,7 +4632,10 @@
> if (NullKind == Expr::NPCK_NotNull)
> return false;
>
> - if (NullKind == Expr::NPCK_ZeroInteger) {
> + if (NullKind == Expr::NPCK_ZeroExpression)
> + return false;
> +
> + if (NullKind == Expr::NPCK_ZeroLiteral) {
> // In this case, check to make sure that we got here from a "NULL"
> // string in the source code.
> NullExpr = NullExpr->IgnoreParenImpCasts();
>
> Modified: cfe/trunk/lib/Sema/SemaOverload.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaOverload.cpp?rev=161501&r1=161500&r2=161501&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaOverload.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaOverload.cpp Wed Aug 8 12:33:31 2012
> @@ -2562,13 +2562,17 @@
>
> Kind = CK_BitCast;
>
> - if (!IsCStyleOrFunctionalCast &&
> - Context.hasSameUnqualifiedType(From->getType(), Context.BoolTy) &&
> - From->isNullPointerConstant(Context, Expr::NPC_ValueDependentIsNotNull))
> - DiagRuntimeBehavior(From->getExprLoc(), From,
> - PDiag(diag::warn_impcast_bool_to_null_pointer)
> - << ToType << From->getSourceRange());
> -
> + if (!IsCStyleOrFunctionalCast && !FromType->isAnyPointerType() &&
> + From->isNullPointerConstant(Context, Expr::NPC_ValueDependentIsNotNull) ==
> + Expr::NPCK_ZeroExpression) {
> + if (Context.hasSameUnqualifiedType(From->getType(), Context.BoolTy))
> + DiagRuntimeBehavior(From->getExprLoc(), From,
> + PDiag(diag::warn_impcast_bool_to_null_pointer)
> + << ToType << From->getSourceRange());
> + else if (!isUnevaluatedContext())
> + Diag(From->getExprLoc(), diag::warn_non_literal_null_pointer)
> + << ToType << From->getSourceRange();
> + }
> if (const PointerType *ToPtrType = ToType->getAs<PointerType>()) {
> if (const PointerType *FromPtrType = FromType->getAs<PointerType>()) {
> QualType FromPointeeType = FromPtrType->getPointeeType(),
>
> Modified: cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp?rev=161501&r1=161500&r2=161501&view=diff
> ==============================================================================
> --- cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp (original)
> +++ cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp Wed Aug 8 12:33:31 2012
> @@ -710,10 +710,16 @@
> static_assert((Base2*)(Derived*)(Base*)pb1 == pok2, "");
> static_assert((Derived*)(Base*)pb1 == (Derived*)pok2, "");
>
> -constexpr Base *nullB = 42 - 6 * 7;
> +constexpr Base *nullB = 42 - 6 * 7; // expected-warning {{expression which evaluates to zero treated as a null pointer constant of type 'Class::Base *const'}}
> static_assert((Bottom*)nullB == 0, "");
> static_assert((Derived*)nullB == 0, "");
> static_assert((void*)(Bottom*)nullB == (void*)(Derived*)nullB, "");
> +Base * nullB2 = '\0'; // expected-warning {{expression which evaluates to zero treated as a null pointer constant of type 'Class::Base *'}}
> +Base * nullB3 = (0);
> +// We suppress the warning in unevaluated contexts to workaround some gtest
> +// behavior. Once this becomes an error this isn't a problem anymore.
> +static_assert(nullB == (1 - 1), "");
> +
>
> namespace ConversionOperators {
>
>
> Modified: cfe/trunk/test/SemaCXX/lambda-expressions.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/lambda-expressions.cpp?rev=161501&r1=161500&r2=161501&view=diff
> ==============================================================================
> --- cfe/trunk/test/SemaCXX/lambda-expressions.cpp (original)
> +++ cfe/trunk/test/SemaCXX/lambda-expressions.cpp Wed Aug 8 12:33:31 2012
> @@ -117,16 +117,16 @@
>
> const int m = 0;
> [=] {
> - int &k = f(m); // a null pointer constant
> + int &k = f(m); // expected-warning{{expression which evaluates to zero treated as a null pointer constant of type 'int *'}}
> } ();
>
> [=] () -> bool {
> - int &k = f(m); // a null pointer constant
> + int &k = f(m); // expected-warning{{expression which evaluates to zero treated as a null pointer constant of type 'int *'}}
> return &m == 0;
> } ();
>
> [m] {
> - int &k = f(m); // a null pointer constant
> + int &k = f(m); // expected-warning{{expression which evaluates to zero treated as a null pointer constant of type 'int *'}}
> } ();
> }
> }
>
> Modified: cfe/trunk/test/SemaTemplate/explicit-instantiation.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaTemplate/explicit-instantiation.cpp?rev=161501&r1=161500&r2=161501&view=diff
> ==============================================================================
> --- cfe/trunk/test/SemaTemplate/explicit-instantiation.cpp (original)
> +++ cfe/trunk/test/SemaTemplate/explicit-instantiation.cpp Wed Aug 8 12:33:31 2012
> @@ -14,7 +14,7 @@
> T f0(T x) {
> return x + 1; // expected-error{{invalid operands}}
> }
> - T* f0(T*, T*) { return T(); }
> + T* f0(T*, T*) { return T(); } // expected-warning{{expression which evaluates to zero treated as a null pointer constant of type 'int *'}}
>
> template<typename U>
> T f0(T, U) { return T(); }
> @@ -32,7 +32,7 @@
> template NotDefaultConstructible X0<NotDefaultConstructible>::value; // expected-note{{instantiation}}
>
> template int X0<int>::f0(int);
> -template int* X0<int>::f0(int*, int*);
> +template int* X0<int>::f0(int*, int*); // expected-note{{in instantiation of member function 'X0<int>::f0' requested here}}
> template int X0<int>::f0(int, float);
>
> template int X0<int>::f0(int) const; // expected-error{{does not refer}}
>
> Modified: cfe/trunk/test/SemaTemplate/instantiate-member-class.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaTemplate/instantiate-member-class.cpp?rev=161501&r1=161500&r2=161501&view=diff
> ==============================================================================
> --- cfe/trunk/test/SemaTemplate/instantiate-member-class.cpp (original)
> +++ cfe/trunk/test/SemaTemplate/instantiate-member-class.cpp Wed Aug 8 12:33:31 2012
> @@ -124,19 +124,20 @@
> {
> struct B
> {
> - struct C { C() { int *ptr = I; } }; // expected-error{{cannot initialize a variable of type 'int *' with an rvalue of type 'int'}}
> + struct C { C() { int *ptr = I; } }; // expected-error{{cannot initialize a variable of type 'int *' with an rvalue of type 'int'}} \
> + expected-warning{{expression which evaluates to zero treated as a null pointer constant of type 'int *'}}
> };
> };
>
> template<int N> void foo()
> {
> - class A<N>::B::C X; // expected-note{{in instantiation of member function}}
> + class A<N>::B::C X; // expected-note 2 {{in instantiation of member function}}
> int A<N+1>::B::C::*member = 0;
> }
>
> void bar()
> {
> - foo<0>();
> + foo<0>(); // expected-note{{in instantiation of function template}}
> foo<1>(); // expected-note{{in instantiation of function template}}
> }
> }
>
>
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