[clang-tools-extra] [clang-tidy] fix false positive for implicit conversion of comparison result in C23 (PR #113639)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-tidy

Author: Congcong Cai (HerrCai0907)

<details>
<summary>Changes</summary>

Fixed #<!-- -->111013
bool will be builtin type in C23 but comparison result in C is still int.
It is no need to change this kind of implicit cast to explicit cast.


---
Full diff: https://github.com/llvm/llvm-project/pull/113639.diff


3 Files Affected:

- (modified) clang-tools-extra/clang-tidy/readability/ImplicitBoolConversionCheck.cpp (+7) 
- (modified) clang-tools-extra/docs/ReleaseNotes.rst (+2-1) 
- (modified) clang-tools-extra/test/clang-tidy/checkers/readability/implicit-bool-conversion.c (+9) 


``````````diff
diff --git a/clang-tools-extra/clang-tidy/readability/ImplicitBoolConversionCheck.cpp b/clang-tools-extra/clang-tidy/readability/ImplicitBoolConversionCheck.cpp
index 968a4a55a6d798..06415c1346a4f0 100644
--- a/clang-tools-extra/clang-tidy/readability/ImplicitBoolConversionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ImplicitBoolConversionCheck.cpp
@@ -26,6 +26,8 @@ AST_MATCHER(Stmt, isMacroExpansion) {
   return SM.isMacroBodyExpansion(Loc) || SM.isMacroArgExpansion(Loc);
 }
 
+AST_MATCHER(Stmt, isC23) { return Finder->getASTContext().getLangOpts().C23; }
+
 bool isNULLMacroExpansion(const Stmt *Statement, ASTContext &Context) {
   SourceManager &SM = Context.getSourceManager();
   const LangOptions &LO = Context.getLangOpts();
@@ -298,6 +300,11 @@ void ImplicitBoolConversionCheck::registerMatchers(MatchFinder *Finder) {
                          hasCastKind(CK_FloatingToBoolean),
                          hasCastKind(CK_PointerToBoolean),
                          hasCastKind(CK_MemberPointerToBoolean)),
+                   // Exclude cases of C23 comparison result.
+                   unless(allOf(
+                       isC23(),
+                       hasSourceExpression(binaryOperator(hasAnyOperatorName(
+                           ">", ">=", "==", "!=", "<", "<="))))),
                    // Exclude case of using if or while statements with variable
                    // declaration, e.g.:
                    //   if (int var = functionCall()) {}
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index a9b1ab367f538a..e42082806fd308 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -244,7 +244,8 @@ Changes in existing checks
 - Improved :doc:`readability-implicit-bool-conversion
   <clang-tidy/checks/readability/implicit-bool-conversion>` check
   by adding the option `UseUpperCaseLiteralSuffix` to select the
-  case of the literal suffix in fixes.
+  case of the literal suffix in fixes and fixing false positive for implicit
+  conversion of comparison result in C23.
 
 - Improved :doc:`readability-redundant-smartptr-get
   <clang-tidy/checks/readability/redundant-smartptr-get>` check to
diff --git a/clang-tools-extra/test/clang-tidy/checkers/readability/implicit-bool-conversion.c b/clang-tools-extra/test/clang-tidy/checkers/readability/implicit-bool-conversion.c
index f3dc32c10d640a..0b231d10adf8fc 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/readability/implicit-bool-conversion.c
+++ b/clang-tools-extra/test/clang-tidy/checkers/readability/implicit-bool-conversion.c
@@ -304,6 +304,15 @@ void implicitConversionToBoolFromUnaryMinusAndZeroLiterals() {
   // CHECK-FIXES: functionTakingBool((-0.0) != 0.0);
 }
 
+void ignoreImplicitCastToBoolForComparisonResult() {
+  bool boolFromComparison0 = 1 != 0;
+  bool boolFromComparison1 = 1 == 0;
+  bool boolFromComparison2 = 1 > 0;
+  bool boolFromComparison3 = 1 >= 0;
+  bool boolFromComparison4 = 1 < 0;
+  bool boolFromComparison5 = 1 <= 0;
+}
+
 void ignoreExplicitCastsToBool() {
   int integer = 10;
   bool boolComingFromInt = (bool)integer;

``````````

</details>


https://github.com/llvm/llvm-project/pull/113639