[clang-tidy] Add enum misuse check.
The checker detects various cases when an enum is probably misused
(as a bitmask).
Patch by: Peter Szecsi!
Differential Revision: https://reviews.llvm.org/D22507
llvm-svn: 290600
diff --git a/clang-tools-extra/clang-tidy/misc/CMakeLists.txt b/clang-tools-extra/clang-tidy/misc/CMakeLists.txt
index 2507772..4014658 100644
--- a/clang-tools-extra/clang-tidy/misc/CMakeLists.txt
+++ b/clang-tools-extra/clang-tidy/misc/CMakeLists.txt
@@ -31,6 +31,7 @@
StringConstructorCheck.cpp
StringIntegerAssignmentCheck.cpp
StringLiteralWithEmbeddedNulCheck.cpp
+ SuspiciousEnumUsageCheck.cpp
SuspiciousMissingCommaCheck.cpp
SuspiciousSemicolonCheck.cpp
SuspiciousStringCompareCheck.cpp
diff --git a/clang-tools-extra/clang-tidy/misc/MiscTidyModule.cpp b/clang-tools-extra/clang-tidy/misc/MiscTidyModule.cpp
index eeef362..0499e06 100644
--- a/clang-tools-extra/clang-tidy/misc/MiscTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/misc/MiscTidyModule.cpp
@@ -38,6 +38,7 @@
#include "StringConstructorCheck.h"
#include "StringIntegerAssignmentCheck.h"
#include "StringLiteralWithEmbeddedNulCheck.h"
+#include "SuspiciousEnumUsageCheck.h"
#include "SuspiciousMissingCommaCheck.h"
#include "SuspiciousSemicolonCheck.h"
#include "SuspiciousStringCompareCheck.h"
@@ -111,6 +112,8 @@
"misc-string-integer-assignment");
CheckFactories.registerCheck<StringLiteralWithEmbeddedNulCheck>(
"misc-string-literal-with-embedded-nul");
+ CheckFactories.registerCheck<SuspiciousEnumUsageCheck>(
+ "misc-suspicious-enum-usage");
CheckFactories.registerCheck<SuspiciousMissingCommaCheck>(
"misc-suspicious-missing-comma");
CheckFactories.registerCheck<SuspiciousSemicolonCheck>(
diff --git a/clang-tools-extra/clang-tidy/misc/SuspiciousEnumUsageCheck.cpp b/clang-tools-extra/clang-tidy/misc/SuspiciousEnumUsageCheck.cpp
new file mode 100644
index 0000000..059c0d2
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/misc/SuspiciousEnumUsageCheck.cpp
@@ -0,0 +1,216 @@
+//===--- SuspiciousEnumUsageCheck.cpp - clang-tidy-------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "SuspiciousEnumUsageCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include <algorithm>
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace misc {
+
+static const char DifferentEnumErrorMessage[] =
+ "enum values are from different enum types";
+
+static const char BitmaskErrorMessage[] =
+ "enum type seems like a bitmask (contains mostly "
+ "power-of-2 literals), but this literal is not a "
+ "power-of-2";
+
+static const char BitmaskVarErrorMessage[] =
+ "enum type seems like a bitmask (contains mostly "
+ "power-of-2 literals) but %plural{1:a literal is|:some literals are}0 not "
+ "power-of-2";
+
+static const char BitmaskNoteMessage[] = "used here as a bitmask";
+
+/// Stores a min and a max value which describe an interval.
+struct ValueRange {
+ llvm::APSInt MinVal;
+ llvm::APSInt MaxVal;
+
+ ValueRange(const EnumDecl *EnumDec) {
+ const auto MinMaxVal = std::minmax_element(
+ EnumDec->enumerator_begin(), EnumDec->enumerator_end(),
+ [](const EnumConstantDecl *E1, const EnumConstantDecl *E2) {
+ return E1->getInitVal() < E2->getInitVal();
+ });
+ MinVal = MinMaxVal.first->getInitVal();
+ MaxVal = MinMaxVal.second->getInitVal();
+ }
+};
+
+/// Return the number of EnumConstantDecls in an EnumDecl.
+static int enumLength(const EnumDecl *EnumDec) {
+ return std::distance(EnumDec->enumerator_begin(), EnumDec->enumerator_end());
+}
+
+static bool hasDisjointValueRange(const EnumDecl *Enum1,
+ const EnumDecl *Enum2) {
+ ValueRange Range1(Enum1), Range2(Enum2);
+ return (Range1.MaxVal < Range2.MinVal) || (Range2.MaxVal < Range1.MinVal);
+}
+
+static bool isNonPowerOf2NorNullLiteral(const EnumConstantDecl *EnumConst) {
+ llvm::APSInt Val = EnumConst->getInitVal();
+ if (Val.isPowerOf2() || !Val.getBoolValue())
+ return false;
+ const Expr *InitExpr = EnumConst->getInitExpr();
+ if (!InitExpr)
+ return true;
+ return isa<IntegerLiteral>(InitExpr->IgnoreImpCasts());
+}
+
+static bool isMaxValAllBitSetLiteral(const EnumDecl *EnumDec) {
+ auto EnumConst = std::max_element(
+ EnumDec->enumerator_begin(), EnumDec->enumerator_end(),
+ [](const EnumConstantDecl *E1, const EnumConstantDecl *E2) {
+ return E1->getInitVal() < E2->getInitVal();
+ });
+
+ if (const Expr *InitExpr = EnumConst->getInitExpr()) {
+ return EnumConst->getInitVal().countTrailingOnes() ==
+ EnumConst->getInitVal().getActiveBits() &&
+ isa<IntegerLiteral>(InitExpr->IgnoreImpCasts());
+ }
+ return false;
+}
+
+static int countNonPowOfTwoLiteralNum(const EnumDecl *EnumDec) {
+ return std::count_if(
+ EnumDec->enumerator_begin(), EnumDec->enumerator_end(),
+ [](const EnumConstantDecl *E) { return isNonPowerOf2NorNullLiteral(E); });
+}
+
+/// Check if there is one or two enumerators that are not a power of 2 and are
+/// initialized by a literal in the enum type, and that the enumeration contains
+/// enough elements to reasonably act as a bitmask. Exclude the case where the
+/// last enumerator is the sum of the lesser values (and initialized by a
+/// literal) or when it could contain consecutive values.
+static bool isPossiblyBitMask(const EnumDecl *EnumDec) {
+ ValueRange VR(EnumDec);
+ int EnumLen = enumLength(EnumDec);
+ int NonPowOfTwoCounter = countNonPowOfTwoLiteralNum(EnumDec);
+ return NonPowOfTwoCounter >= 1 && NonPowOfTwoCounter <= 2 &&
+ NonPowOfTwoCounter < EnumLen / 2 &&
+ (VR.MaxVal - VR.MinVal != EnumLen - 1) &&
+ !(NonPowOfTwoCounter == 1 && isMaxValAllBitSetLiteral(EnumDec));
+}
+
+SuspiciousEnumUsageCheck::SuspiciousEnumUsageCheck(StringRef Name,
+ ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context), StrictMode(Options.get("StrictMode", 0)) {}
+
+void SuspiciousEnumUsageCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+ Options.store(Opts, "StrictMode", StrictMode);
+}
+
+void SuspiciousEnumUsageCheck::registerMatchers(MatchFinder *Finder) {
+ const auto enumExpr = [](StringRef RefName, StringRef DeclName) {
+ return allOf(ignoringImpCasts(expr().bind(RefName)),
+ ignoringImpCasts(hasType(enumDecl().bind(DeclName))));
+ };
+
+ Finder->addMatcher(
+ binaryOperator(hasOperatorName("|"), hasLHS(enumExpr("", "enumDecl")),
+ hasRHS(allOf(enumExpr("", "otherEnumDecl"),
+ ignoringImpCasts(hasType(enumDecl(
+ unless(equalsBoundNode("enumDecl"))))))))
+ .bind("diffEnumOp"),
+ this);
+
+ Finder->addMatcher(
+ binaryOperator(anyOf(hasOperatorName("+"), hasOperatorName("|")),
+ hasLHS(enumExpr("lhsExpr", "enumDecl")),
+ hasRHS(allOf(enumExpr("rhsExpr", ""),
+ ignoringImpCasts(hasType(enumDecl(
+ equalsBoundNode("enumDecl"))))))),
+ this);
+
+ Finder->addMatcher(
+ binaryOperator(anyOf(hasOperatorName("+"), hasOperatorName("|")),
+ hasEitherOperand(
+ allOf(hasType(isInteger()), unless(enumExpr("", "")))),
+ hasEitherOperand(enumExpr("enumExpr", "enumDecl"))),
+ this);
+
+ Finder->addMatcher(
+ binaryOperator(anyOf(hasOperatorName("|="), hasOperatorName("+=")),
+ hasRHS(enumExpr("enumExpr", "enumDecl"))),
+ this);
+}
+
+void SuspiciousEnumUsageCheck::checkSuspiciousBitmaskUsage(
+ const Expr *NodeExpr, const EnumDecl *EnumDec) {
+ const auto *EnumExpr = dyn_cast<DeclRefExpr>(NodeExpr);
+ const auto *EnumConst =
+ EnumExpr ? dyn_cast<EnumConstantDecl>(EnumExpr->getDecl()) : nullptr;
+
+ // Report the parameter if neccessary.
+ if (!EnumConst) {
+ diag(EnumDec->getInnerLocStart(), BitmaskVarErrorMessage)
+ << countNonPowOfTwoLiteralNum(EnumDec);
+ diag(EnumExpr->getExprLoc(), BitmaskNoteMessage, DiagnosticIDs::Note);
+ } else if (isNonPowerOf2NorNullLiteral(EnumConst)) {
+ diag(EnumConst->getSourceRange().getBegin(), BitmaskErrorMessage);
+ diag(EnumExpr->getExprLoc(), BitmaskNoteMessage, DiagnosticIDs::Note);
+ }
+}
+
+void SuspiciousEnumUsageCheck::check(const MatchFinder::MatchResult &Result) {
+ // Case 1: The two enum values come from different types.
+ if (const auto *DiffEnumOp =
+ Result.Nodes.getNodeAs<BinaryOperator>("diffEnumOp")) {
+ const auto *EnumDec = Result.Nodes.getNodeAs<EnumDecl>("enumDecl");
+ const auto *OtherEnumDec =
+ Result.Nodes.getNodeAs<EnumDecl>("otherEnumDecl");
+ // Skip when one of the parameters is an empty enum. The
+ // hasDisjointValueRange function could not decide the values properly in
+ // case of an empty enum.
+ if (EnumDec->enumerator_begin() == EnumDec->enumerator_end() ||
+ OtherEnumDec->enumerator_begin() == OtherEnumDec->enumerator_end())
+ return;
+
+ if (!hasDisjointValueRange(EnumDec, OtherEnumDec))
+ diag(DiffEnumOp->getOperatorLoc(), DifferentEnumErrorMessage);
+ return;
+ }
+
+ // Case 2 and 3 only checked in strict mode. The checker tries to detect
+ // suspicious bitmasks which contains values initialized by non power-of-2
+ // literals.
+ if (!StrictMode)
+ return;
+ const auto *EnumDec = Result.Nodes.getNodeAs<EnumDecl>("enumDecl");
+ if (!isPossiblyBitMask(EnumDec))
+ return;
+
+ // Case 2:
+ // a. Investigating the right hand side of `+=` or `|=` operator.
+ // b. When the operator is `|` or `+` but only one of them is an EnumExpr
+ if (const auto *EnumExpr = Result.Nodes.getNodeAs<Expr>("enumExpr")) {
+ checkSuspiciousBitmaskUsage(EnumExpr, EnumDec);
+ return;
+ }
+
+ // Case 3:
+ // '|' or '+' operator where both argument comes from the same enum type
+ const auto *LhsExpr = Result.Nodes.getNodeAs<Expr>("lhsExpr");
+ checkSuspiciousBitmaskUsage(LhsExpr, EnumDec);
+
+ const auto *RhsExpr = Result.Nodes.getNodeAs<Expr>("rhsExpr");
+ checkSuspiciousBitmaskUsage(RhsExpr, EnumDec);
+}
+
+} // namespace misc
+} // namespace tidy
+} // namespace clang
diff --git a/clang-tools-extra/clang-tidy/misc/SuspiciousEnumUsageCheck.h b/clang-tools-extra/clang-tidy/misc/SuspiciousEnumUsageCheck.h
new file mode 100644
index 0000000..d532179
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/misc/SuspiciousEnumUsageCheck.h
@@ -0,0 +1,39 @@
+//===--- SuspiciousEnumUsageCheck.h - clang-tidy--------------------------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_SUSPICIOUS_ENUM_USAGE_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_SUSPICIOUS_ENUM_USAGE_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace misc {
+
+/// The checker detects various cases when an enum is probably misused (as a
+/// bitmask).
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/misc-suspicious-enum-usage.html
+class SuspiciousEnumUsageCheck : public ClangTidyCheck {
+public:
+ SuspiciousEnumUsageCheck(StringRef Name, ClangTidyContext *Context);
+ void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+ void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+ void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
+
+private:
+ void checkSuspiciousBitmaskUsage(const Expr*, const EnumDecl*);
+ const bool StrictMode;
+};
+
+} // namespace misc
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_SUSPICIOUS_ENUM_USAGE_H