Fix the issue #139467 ([clang-tidy] false positive narrowing conversion) #139474
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@llvm/pr-subscribers-clang-tidy @llvm/pr-subscribers-clang-tools-extra Author: Andrey (AndreyG) ChangesLet's consider the following code from the issue #139467: void test(int cond, char c) {
char ret = cond > 0 ? ':' : c;
}Initializer of So it could be seen that Full diff: https://github.com/llvm/llvm-project/pull/139474.diff 3 Files Affected:
diff --git a/clang-tools-extra/clang-tidy/bugprone/NarrowingConversionsCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/NarrowingConversionsCheck.cpp
index bafcd402ca851..9e53bfe83e03e 100644
--- a/clang-tools-extra/clang-tidy/bugprone/NarrowingConversionsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/NarrowingConversionsCheck.cpp
@@ -554,15 +554,23 @@ bool NarrowingConversionsCheck::handleConditionalOperator(
// We have an expression like so: `output = cond ? lhs : rhs`
// From the point of view of narrowing conversion we treat it as two
// expressions `output = lhs` and `output = rhs`.
- handleBinaryOperator(Context, CO->getLHS()->getExprLoc(), Lhs,
- *CO->getLHS());
- handleBinaryOperator(Context, CO->getRHS()->getExprLoc(), Lhs,
- *CO->getRHS());
+ handleConditionalOperatorArgument(Context, Lhs, CO->getLHS());
+ handleConditionalOperatorArgument(Context, Lhs, CO->getRHS());
return true;
}
return false;
}
+void NarrowingConversionsCheck::handleConditionalOperatorArgument(
+ const ASTContext &Context, const Expr &Lhs, const Expr *Arg) {
+ if (const auto *ICE = llvm::dyn_cast<ImplicitCastExpr>(Arg)) {
+ if (!Arg->getIntegerConstantExpr(Context)) {
+ Arg = ICE->getSubExpr();
+ }
+ }
+ handleBinaryOperator(Context, Arg->getExprLoc(), Lhs, *Arg);
+}
+
void NarrowingConversionsCheck::handleImplicitCast(
const ASTContext &Context, const ImplicitCastExpr &Cast) {
if (Cast.getExprLoc().isMacroID())
diff --git a/clang-tools-extra/clang-tidy/bugprone/NarrowingConversionsCheck.h b/clang-tools-extra/clang-tidy/bugprone/NarrowingConversionsCheck.h
index 20403f920b925..ebddbc2869675 100644
--- a/clang-tools-extra/clang-tidy/bugprone/NarrowingConversionsCheck.h
+++ b/clang-tools-extra/clang-tidy/bugprone/NarrowingConversionsCheck.h
@@ -85,6 +85,8 @@ class NarrowingConversionsCheck : public ClangTidyCheck {
bool handleConditionalOperator(const ASTContext &Context, const Expr &Lhs,
const Expr &Rhs);
+ void handleConditionalOperatorArgument(const ASTContext &Context, const Expr &Lhs,
+ const Expr *Arg);
void handleImplicitCast(const ASTContext &Context,
const ImplicitCastExpr &Cast);
diff --git a/clang-tools-extra/test/clang-tidy/checkers/bugprone/narrowing-conversions-conditional-expressions.c b/clang-tools-extra/test/clang-tidy/checkers/bugprone/narrowing-conversions-conditional-expressions.c
new file mode 100644
index 0000000000000..754d6425b07cd
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone/narrowing-conversions-conditional-expressions.c
@@ -0,0 +1,6 @@
+// RUN: %check_clang_tidy %s bugprone-narrowing-conversions %t -- --
+
+char test(int cond, char c) {
+ char ret = cond > 0 ? ':' : c;
+ return ret;
+}
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Please mention changes in Release Notes. |
| if (const auto *ICE = llvm::dyn_cast<ImplicitCastExpr>(Arg)) { | ||
| if (!Arg->getIntegerConstantExpr(Context)) { | ||
| Arg = ICE->getSubExpr(); | ||
| } | ||
| } |
There was a problem hiding this comment.
As per LLVM coding-style, there shouldn't be any braces for single-stmt ifs.
if (const auto *ICE = llvm::dyn_cast<ImplicitCastExpr>(Arg))
if (!Arg->getIntegerConstantExpr(Context))
Arg = ICE->getSubExpr();There was a problem hiding this comment.
Let's consider the following code from the issue llvm#139467: void test(int cond, char c) { char ret = cond > 0 ? ':' : c; } Initializer of 'ret' looks the following: -ImplicitCastExpr 'char' <IntegralCast> `-ConditionalOperator 'int' |-BinaryOperator 'int' '>' | |-ImplicitCastExpr 'int' <LValueToRValue> | | `-DeclRefExpr 'int' lvalue ParmVar 'cond' 'int' | `-IntegerLiteral 'int' 0 |-CharacterLiteral 'int' 58 `-ImplicitCastExpr 'int' <IntegralCast> `-ImplicitCastExpr 'char' <LValueToRValue> `-DeclRefExpr 'char' lvalue ParmVar 'c' 'char' So it could be seen that 'RHS' of the conditional operator is DeclRefExpr 'c' which is casted to 'int' and then the whole conditional expression is casted to 'char'. But this last conversion is not narrowing, because 'RHS' was 'char' _initially_. We should just remove the cast from 'char' to 'int' before the narrowing conversion check.
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Let's consider the following code from the issue #139467:
Initializer of
retlooks the following:So it could be seen that
RHSof the conditional operator isDeclRefExpr 'c'which is casted tointand then the whole conditional expression is casted to 'char'. But this last conversion is not narrowing, becauseRHSwascharinitially. We should just remove the cast fromchartointbefore the narrowing conversion check.