[clang-tidy] Add a checker for implicit bool conversion of a bool*.
The goal is to find code like the example below, which is likely a typo
where someone meant to write "if (*b)".
bool *b = SomeFunction();
if (b) {
// b never dereferenced
}
This checker naturally has a relatively high false positive rate so it
applies some heuristics to avoid cases where the pointer is checked for
nullptr before being written.
Differential Revision: http://reviews.llvm.org/D4458
llvm-svn: 212797
diff --git a/clang-tools-extra/clang-tidy/misc/BoolPointerImplicitConversion.cpp b/clang-tools-extra/clang-tidy/misc/BoolPointerImplicitConversion.cpp
new file mode 100644
index 0000000..6565874
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/misc/BoolPointerImplicitConversion.cpp
@@ -0,0 +1,70 @@
+//===--- BoolPointerImplicitConversion.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 "BoolPointerImplicitConversion.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace ast_matchers {
+
+AST_MATCHER(CastExpr, isPointerToBoolean) {
+ return Node.getCastKind() == CK_PointerToBoolean;
+}
+AST_MATCHER(QualType, isBoolean) { return Node->isBooleanType(); }
+
+} // namespace ast_matchers
+
+namespace tidy {
+
+void BoolPointerImplicitConversion::registerMatchers(MatchFinder *Finder) {
+ // Look for ifs that have an implicit bool* to bool conversion in the
+ // condition. Filter negations.
+ Finder->addMatcher(
+ ifStmt(hasCondition(findAll(implicitCastExpr(
+ allOf(unless(hasParent(unaryOperator(hasOperatorName("!")))),
+ hasSourceExpression(expr(
+ hasType(pointerType(pointee(isBoolean()))),
+ ignoringParenImpCasts(declRefExpr().bind("expr")))),
+ isPointerToBoolean()))))).bind("if"),
+ this);
+}
+
+void
+BoolPointerImplicitConversion::check(const MatchFinder::MatchResult &Result) {
+ auto *If = Result.Nodes.getStmtAs<IfStmt>("if");
+ auto *Var = Result.Nodes.getStmtAs<DeclRefExpr>("expr");
+
+ // Only allow variable accesses for now, no function calls or member exprs.
+ // Check that we don't dereference the variable anywhere within the if. This
+ // avoids false positives for checks of the pointer for nullptr before it is
+ // dereferenced. If there is a dereferencing operator on this variable don't
+ // emit a diagnostic. Also ignore array subscripts.
+ const Decl *D = Var->getDecl();
+ auto DeclRef = ignoringParenImpCasts(declRefExpr(to(equalsNode(D))));
+ if (!match(findAll(
+ unaryOperator(hasOperatorName("*"), hasUnaryOperand(DeclRef))),
+ *If, *Result.Context).empty() ||
+ !match(findAll(arraySubscriptExpr(hasBase(DeclRef))), *If,
+ *Result.Context).empty() ||
+ // FIXME: We should still warn if the paremater is implicitly converted to
+ // bool.
+ !match(findAll(callExpr(hasAnyArgument(DeclRef))), *If, *Result.Context)
+ .empty() ||
+ !match(findAll(deleteExpr(has(expr(DeclRef)))), *If, *Result.Context)
+ .empty())
+ return;
+
+ diag(Var->getLocStart(), "dubious check of 'bool *' against 'nullptr', did "
+ "you mean to dereference it?")
+ << FixItHint::CreateInsertion(Var->getLocStart(), "*");
+}
+
+} // namespace tidy
+} // namespace clang