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