r367940 - [Sema] Add -Wpointer-compare
George Burgess IV via cfe-commits
cfe-commits at lists.llvm.org
Mon Aug 5 15:15:40 PDT 2019
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 at -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';
+}
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