rtrieu updated this revision to Diff 214733.
rtrieu added a comment.
Create new function isIntOrEnumConstantZero to use instead of EvaluateAsInt
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D66046/new/
https://reviews.llvm.org/D66046
Files:
include/clang/Analysis/CFG.h
include/clang/Basic/DiagnosticGroups.td
include/clang/Basic/DiagnosticSemaKinds.td
lib/Analysis/CFG.cpp
lib/Sema/AnalysisBasedWarnings.cpp
test/Sema/warn-bitwise-compare.c
test/SemaCXX/warn-bitwise-compare.cpp
Index: test/SemaCXX/warn-bitwise-compare.cpp
===================================================================
--- test/SemaCXX/warn-bitwise-compare.cpp
+++ test/SemaCXX/warn-bitwise-compare.cpp
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -Wtautological-bitwise-compare %s
+
+void test(int x) {
+ bool b1 = (8 & x) == 3;
+ // expected-warning@-1 {{bitwise comparison always evaluates to false}}
+ bool b2 = x | 5;
+ // expected-warning@-1 {{bitwise or with non-zero value always evaluates to true}}
+ bool b3 = (x | 5);
+ // expected-warning@-1 {{bitwise or with non-zero value always evaluates to true}}
+ bool b4 = !!(x | 5);
+ // expected-warning@-1 {{bitwise or with non-zero value always evaluates to true}}
+}
Index: test/Sema/warn-bitwise-compare.c
===================================================================
--- test/Sema/warn-bitwise-compare.c
+++ test/Sema/warn-bitwise-compare.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -Wtautological-compare %s
+// RUN: %clang_cc1 -fsyntax-only -verify -Wtautological-bitwise-compare %s
#define mydefine 2
@@ -13,6 +13,9 @@
if ((x & 0x15) == 0x13) {} // expected-warning {{bitwise comparison always evaluates to false}}
if ((0x23 | x) == 0x155){} // expected-warning {{bitwise comparison always evaluates to false}}
+ if (!!((8 & x) == 3)) {} // expected-warning {{bitwise comparison always evaluates to false}}
+ int y = ((8 & x) == 3) ? 1 : 2; // expected-warning {{bitwise comparison always evaluates to false}}
+
if ((x & 8) == 8) {}
if ((x & 8) != 8) {}
if ((x | 4) == 4) {}
@@ -26,3 +29,9 @@
if ((x & mydefine) == 8) {}
if ((x | mydefine) == 4) {}
}
+
+void g(int x) {
+ if (x | 5) {} // expected-warning {{bitwise or with non-zero value always evaluates to true}}
+ if (5 | x) {} // expected-warning {{bitwise or with non-zero value always evaluates to true}}
+ if (!((x | 5))) {} // expected-warning {{bitwise or with non-zero value always evaluates to true}}
+}
Index: lib/Sema/AnalysisBasedWarnings.cpp
===================================================================
--- lib/Sema/AnalysisBasedWarnings.cpp
+++ lib/Sema/AnalysisBasedWarnings.cpp
@@ -159,6 +159,20 @@
S.Diag(B->getExprLoc(), diag::warn_comparison_bitwise_always)
<< DiagRange << isAlwaysTrue;
}
+
+ void compareBitwiseOr(const BinaryOperator *B) override {
+ if (HasMacroID(B))
+ return;
+
+ SourceRange DiagRange = B->getSourceRange();
+ S.Diag(B->getExprLoc(), diag::warn_comparison_bitwise_or) << DiagRange;
+ }
+
+ static bool hasActiveDiagnostics(DiagnosticsEngine &Diags,
+ SourceLocation Loc) {
+ return !Diags.isIgnored(diag::warn_tautological_overlap_comparison, Loc) ||
+ !Diags.isIgnored(diag::warn_comparison_bitwise_or, Loc);
+ }
};
} // anonymous namespace
@@ -2076,10 +2090,9 @@
.setAlwaysAdd(Stmt::AttributedStmtClass);
}
- // Install the logical handler for -Wtautological-overlap-compare
+ // Install the logical handler.
llvm::Optional<LogicalErrorHandler> LEH;
- if (!Diags.isIgnored(diag::warn_tautological_overlap_comparison,
- D->getBeginLoc())) {
+ if (LogicalErrorHandler::hasActiveDiagnostics(Diags, D->getBeginLoc())) {
LEH.emplace(S);
AC.getCFGBuildOptions().Observer = &*LEH;
}
@@ -2228,9 +2241,8 @@
checkThrowInNonThrowingFunc(S, FD, AC);
// If none of the previous checks caused a CFG build, trigger one here
- // for -Wtautological-overlap-compare
- if (!Diags.isIgnored(diag::warn_tautological_overlap_comparison,
- D->getBeginLoc())) {
+ // for the logical error handler.
+ if (LogicalErrorHandler::hasActiveDiagnostics(Diags, D->getBeginLoc())) {
AC.getCFG();
}
Index: lib/Analysis/CFG.cpp
===================================================================
--- lib/Analysis/CFG.cpp
+++ lib/Analysis/CFG.cpp
@@ -81,6 +81,20 @@
return nullptr;
}
+/// Takes an expression returned from tryTransformToIntOrEnumConstant and
+/// evaluates its non-zeroness.
+static bool isIntOrEnumConstantZero(const Expr *E) {
+ E = E->IgnoreParens();
+ if (const auto *Integer = dyn_cast<IntegerLiteral>(E))
+ return Integer->getValue() == 0;
+
+ // These are non-null because they have been checked in
+ // tryTransformToIntOrEnumConstant
+ const auto *DR = cast<DeclRefExpr>(E->IgnoreParenImpCasts());
+ const auto *EC = cast<EnumConstantDecl>(DR->getDecl());
+ return EC->getInitVal() == 0;
+}
+
/// Tries to interpret a binary operator into `Decl Op Expr` form, if Expr is
/// an integer literal or an enum constant.
///
@@ -1102,6 +1116,27 @@
return {};
}
+ /// A bitwise-or with a non-zero constant always evaluates to true.
+ TryResult checkIncorrectBitwiseOrOperator(const BinaryOperator *B) {
+ const Expr *LHSConstant =
+ tryTransformToIntOrEnumConstant(B->getLHS()->IgnoreParenImpCasts());
+ const Expr *RHSConstant =
+ tryTransformToIntOrEnumConstant(B->getRHS()->IgnoreParenImpCasts());
+
+ if ((LHSConstant && RHSConstant) || (!LHSConstant && !RHSConstant))
+ return {};
+
+ const Expr *Constant = LHSConstant ? LHSConstant : RHSConstant;
+
+ if (isIntOrEnumConstantZero(Constant))
+ return {};
+
+ if (BuildOpts.Observer)
+ BuildOpts.Observer->compareBitwiseOr(B);
+
+ return TryResult(true);
+ }
+
/// Try and evaluate an expression to an integer constant.
bool tryEvaluate(Expr *S, Expr::EvalResult &outResult) {
if (!BuildOpts.PruneTriviallyFalseEdges)
@@ -1119,7 +1154,7 @@
return {};
if (BinaryOperator *Bop = dyn_cast<BinaryOperator>(S)) {
- if (Bop->isLogicalOp()) {
+ if (Bop->isLogicalOp() || Bop->isEqualityOp()) {
// Check the cache first.
CachedBoolEvalsTy::iterator I = CachedBoolEvals.find(S);
if (I != CachedBoolEvals.end())
@@ -1203,6 +1238,10 @@
TryResult BopRes = checkIncorrectRelationalOperator(Bop);
if (BopRes.isKnown())
return BopRes.isTrue();
+ } else if (Bop->getOpcode() == BO_Or) {
+ TryResult BopRes = checkIncorrectBitwiseOrOperator(Bop);
+ if (BopRes.isKnown())
+ return BopRes.isTrue();
}
}
@@ -2301,6 +2340,9 @@
appendStmt(Block, U);
}
+ if (U->getOpcode() == UO_LNot)
+ tryEvaluateBool(U->getSubExpr()->IgnoreParens());
+
return Visit(U->getSubExpr(), AddStmtChoice());
}
@@ -2435,6 +2477,9 @@
appendStmt(Block, B);
}
+ if (B->isEqualityOp() || B->isRelationalOp())
+ tryEvaluateBool(B);
+
CFGBlock *RBlock = Visit(B->getRHS());
CFGBlock *LBlock = Visit(B->getLHS());
// If visiting RHS causes us to finish 'Block', e.g. the RHS is a StmtExpr
@@ -4477,6 +4522,10 @@
autoCreateBlock();
appendStmt(Block, E);
}
+
+ if (E->getCastKind() == CK_IntegralToBoolean)
+ tryEvaluateBool(E->getSubExpr()->IgnoreParens());
+
return Visit(E->getSubExpr(), AddStmtChoice());
}
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -8155,7 +8155,10 @@
InGroup<TautologicalCompare>;
def warn_comparison_bitwise_always : Warning<
"bitwise comparison always evaluates to %select{false|true}0">,
- InGroup<TautologicalCompare>;
+ InGroup<TautologicalBitwiseCompare>, DefaultIgnore;
+def warn_comparison_bitwise_or : Warning<
+ "bitwise or with non-zero value always evaluates to true">,
+ InGroup<TautologicalBitwiseCompare>, DefaultIgnore;
def warn_tautological_overlap_comparison : Warning<
"overlapping comparisons always evaluate to %select{false|true}0">,
InGroup<TautologicalOverlapCompare>, DefaultIgnore;
Index: include/clang/Basic/DiagnosticGroups.td
===================================================================
--- include/clang/Basic/DiagnosticGroups.td
+++ include/clang/Basic/DiagnosticGroups.td
@@ -498,12 +498,14 @@
[TautologicalOutOfRangeCompare]>;
def TautologicalPointerCompare : DiagGroup<"tautological-pointer-compare">;
def TautologicalOverlapCompare : DiagGroup<"tautological-overlap-compare">;
+def TautologicalBitwiseCompare : DiagGroup<"tautological-bitwise-compare">;
def TautologicalUndefinedCompare : DiagGroup<"tautological-undefined-compare">;
def TautologicalObjCBoolCompare : DiagGroup<"tautological-objc-bool-compare">;
def TautologicalCompare : DiagGroup<"tautological-compare",
[TautologicalConstantCompare,
TautologicalPointerCompare,
TautologicalOverlapCompare,
+ TautologicalBitwiseCompare,
TautologicalUndefinedCompare,
TautologicalObjCBoolCompare]>;
def HeaderHygiene : DiagGroup<"header-hygiene">;
Index: include/clang/Analysis/CFG.h
===================================================================
--- include/clang/Analysis/CFG.h
+++ include/clang/Analysis/CFG.h
@@ -1023,6 +1023,7 @@
virtual void compareAlwaysTrue(const BinaryOperator *B, bool isAlwaysTrue) {}
virtual void compareBitwiseEquality(const BinaryOperator *B,
bool isAlwaysTrue) {}
+ virtual void compareBitwiseOr(const BinaryOperator *B) {}
};
/// Represents a source-level, intra-procedural CFG that represents the
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