This seems a bit narrow - could it be generalized to all cases of '\0' as a null pointer?
On Mon, Aug 5, 2019 at 3:14 PM George Burgess IV via cfe-commits < cfe-commits@lists.llvm.org> wrote: > Author: gbiv > Date: Mon Aug 5 15:15:40 2019 > New Revision: 367940 > > URL: http://llvm.org/viewvc/llvm-project?rev=367940&view=rev > Log: > [Sema] Add -Wpointer-compare > > This patch adds a warning that diagnoses comparisons of pointers to > '\0'. This is often indicative of a bug (e.g. the user might've > forgotten to dereference the pointer). > > Patch by Elaina Guan! > > Differential Revision: https://reviews.llvm.org/D65595 > > Added: > cfe/trunk/test/Sema/warn-nullchar-nullptr.c > Modified: > cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td > cfe/trunk/include/clang/Sema/Sema.h > cfe/trunk/lib/Sema/SemaExpr.cpp > > Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=367940&r1=367939&r2=367940&view=diff > > ============================================================================== > --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original) > +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Mon Aug 5 > 15:15:40 2019 > @@ -3296,6 +3296,10 @@ def warn_impcast_bool_to_null_pointer : > 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_pointer_compare : Warning< > + "comparing a pointer to a null character constant; did you mean " > + "to compare to %select{NULL|(void *)0}0?">, > + InGroup<DiagGroup<"pointer-compare">>; > def warn_impcast_null_pointer_to_integer : Warning< > "implicit conversion of %select{NULL|nullptr}0 constant to %1">, > InGroup<NullConversion>; > > Modified: cfe/trunk/include/clang/Sema/Sema.h > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Sema/Sema.h?rev=367940&r1=367939&r2=367940&view=diff > > ============================================================================== > --- cfe/trunk/include/clang/Sema/Sema.h (original) > +++ cfe/trunk/include/clang/Sema/Sema.h Mon Aug 5 15:15:40 2019 > @@ -10022,6 +10022,7 @@ public: > QualType CheckShiftOperands( // C99 6.5.7 > ExprResult &LHS, ExprResult &RHS, SourceLocation Loc, > BinaryOperatorKind Opc, bool IsCompAssign = false); > + void CheckPtrComparisonWithNullChar(ExprResult &E, ExprResult &NullE); > QualType CheckCompareOperands( // C99 6.5.8/9 > ExprResult &LHS, ExprResult &RHS, SourceLocation Loc, > BinaryOperatorKind Opc); > > Modified: cfe/trunk/lib/Sema/SemaExpr.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=367940&r1=367939&r2=367940&view=diff > > ============================================================================== > --- cfe/trunk/lib/Sema/SemaExpr.cpp (original) > +++ cfe/trunk/lib/Sema/SemaExpr.cpp Mon Aug 5 15:15:40 2019 > @@ -10443,6 +10443,32 @@ static QualType checkArithmeticOrEnumera > return S.Context.getLogicalOperationType(); > } > > +void Sema::CheckPtrComparisonWithNullChar(ExprResult &E, ExprResult > &NullE) { > + if (!NullE.get()->getType()->isAnyPointerType()) > + return; > + int NullValue = PP.isMacroDefined("NULL") ? 0 : 1; > + if (!E.get()->getType()->isAnyPointerType() && > + E.get()->isNullPointerConstant(Context, > + Expr::NPC_ValueDependentIsNotNull) == > + Expr::NPCK_ZeroExpression) { > + if (const auto *CL = dyn_cast<CharacterLiteral>(E.get())) { > + if (CL->getValue() == 0) > + Diag(E.get()->getExprLoc(), diag::warn_pointer_compare) > + << NullValue > + << FixItHint::CreateReplacement(E.get()->getExprLoc(), > + NullValue ? "NULL" : "(void > *)0"); > + } else if (const auto *CE = dyn_cast<CStyleCastExpr>(E.get())) { > + TypeSourceInfo *TI = CE->getTypeInfoAsWritten(); > + QualType T = > Context.getCanonicalType(TI->getType()).getUnqualifiedType(); > + if (T == Context.CharTy) > + Diag(E.get()->getExprLoc(), diag::warn_pointer_compare) > + << NullValue > + << FixItHint::CreateReplacement(E.get()->getExprLoc(), > + NullValue ? "NULL" : "(void > *)0"); > + } > + } > +} > + > // C99 6.5.8, C++ [expr.rel] > QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS, > SourceLocation Loc, > @@ -10476,6 +10502,10 @@ QualType Sema::CheckCompareOperands(Expr > } > > checkArithmeticNull(*this, LHS, RHS, Loc, /*IsCompare=*/true); > + if (!getLangOpts().CPlusPlus && BinaryOperator::isEqualityOp(Opc)) { > + CheckPtrComparisonWithNullChar(LHS, RHS); > + CheckPtrComparisonWithNullChar(RHS, LHS); > + } > > // Handle vector comparisons separately. > if (LHS.get()->getType()->isVectorType() || > > Added: cfe/trunk/test/Sema/warn-nullchar-nullptr.c > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/warn-nullchar-nullptr.c?rev=367940&view=auto > > ============================================================================== > --- cfe/trunk/test/Sema/warn-nullchar-nullptr.c (added) > +++ cfe/trunk/test/Sema/warn-nullchar-nullptr.c Mon Aug 5 15:15:40 2019 > @@ -0,0 +1,49 @@ > +// RUN: %clang_cc1 -fsyntax-only -verify -Wall %s > + > +int test1(int *a) { > + return a == '\0'; // expected-warning {{comparing a pointer to a null > character constant; did you mean to compare to (void *)0?}} > +} > + > +int test2(int *a) { > + return '\0' == a; // expected-warning {{comparing a pointer to a null > character constant; did you mean to compare to (void *)0?}} > +} > + > +int test3(int *a) { > + return a == L'\0'; // expected-warning {{comparing a pointer to a null > character constant; did you mean to compare to (void *)0?}} > +} > + > +int test4(int *a) { > + return a == u'\0'; // expected-warning {{comparing a pointer to a null > character constant; did you mean to compare to (void *)0?}} > +} > + > +int test5(int *a) { > + return a == U'\0'; // expected-warning {{comparing a pointer to a null > character constant; did you mean to compare to (void *)0?}} > +} > + > +int test6(int *a) { > + return a == (char)0; // expected-warning {{comparing a pointer to a > null character constant; did you mean to compare to (void *)0?}} > +} > + > +typedef char my_char; > +int test7(int *a) { > + return a == (my_char)0; > + // expected-warning@-1 {{comparing a pointer to a null character > constant; did you mean to compare to (void *)0?}} > +} > + > +int test8(int *a) { > + return a != '\0'; // expected-warning {{comparing a pointer to a null > character constant; did you mean to compare to (void *)0?}} > +} > + > +#define NULL (void *)0 > +int test9(int *a) { > + return a == '\0'; // expected-warning {{comparing a pointer to a null > character constant; did you mean to compare to NULL?}} > +} > + > +#define MYCHAR char > +int test10(int *a) { > + return a == (MYCHAR)0; // expected-warning {{comparing a pointer to a > null character constant; did you mean to compare to NULL?}} > +} > + > +int test11(int *a) { > + return a > '\0'; > +} > > > _______________________________________________ > cfe-commits mailing list > cfe-commits@lists.llvm.org > https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits >
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