From a27ae544f30bfd7dc765b8a6080190d39d893b99 Mon Sep 17 00:00:00 2001 From: Richard Trieu Date: Sat, 19 Oct 2019 00:57:23 +0000 Subject: New tautological warning for bitwise-or with non-zero constant always true. Taking a value and the bitwise-or it with a non-zero constant will always result in a non-zero value. In a boolean context, this is always true. if (x | 0x4) {} // always true, intended '&' This patch creates a new warning group -Wtautological-bitwise-compare for this warning. It also moves in the existing tautological bitwise comparisons into this group. A few other changes were needed to the CFGBuilder so that all bool contexts would be checked. The warnings in -Wtautological-bitwise-compare will be off by default due to using the CFG. Fixes: https://bugs.llvm.org/show_bug.cgi?id=42666 Differential Revision: https://reviews.llvm.org/D66046 git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@375318 91177308-0d34-0410-b5e6-96231b3b80d8 --- include/clang/Analysis/CFG.h | 1 + include/clang/Basic/DiagnosticGroups.td | 2 ++ include/clang/Basic/DiagnosticSemaKinds.td | 5 ++++- 3 files changed, 7 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/clang/Analysis/CFG.h b/include/clang/Analysis/CFG.h index b24e32c966..a8301a0e00 100644 --- a/include/clang/Analysis/CFG.h +++ b/include/clang/Analysis/CFG.h @@ -1213,6 +1213,7 @@ public: 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 diff --git a/include/clang/Basic/DiagnosticGroups.td b/include/clang/Basic/DiagnosticGroups.td index 396f297881..3573ebdfc6 100644 --- a/include/clang/Basic/DiagnosticGroups.td +++ b/include/clang/Basic/DiagnosticGroups.td @@ -516,12 +516,14 @@ def TautologicalConstantCompare : DiagGroup<"tautological-constant-compare", [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">; diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td index e41cfe2fe7..98fce04e66 100644 --- a/include/clang/Basic/DiagnosticSemaKinds.td +++ b/include/clang/Basic/DiagnosticSemaKinds.td @@ -8332,7 +8332,10 @@ def warn_comparison_always : Warning< InGroup; def warn_comparison_bitwise_always : Warning< "bitwise comparison always evaluates to %select{false|true}0">, - InGroup; + InGroup, DefaultIgnore; +def warn_comparison_bitwise_or : Warning< + "bitwise or with non-zero value always evaluates to true">, + InGroup, DefaultIgnore; def warn_tautological_overlap_comparison : Warning< "overlapping comparisons always evaluate to %select{false|true}0">, InGroup, DefaultIgnore; -- cgit v1.2.1