[clang-tools-extra] [clang-tidy]: Ignore empty `catch` blocks in destructors in `bugprone-empty-catch` check (PR #161379)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-tools-extra

Author: Andrey Karlov (negativ)

<details>
<summary>Changes</summary>

While flagging empty `catch` blocks is generally a great rule, it produces false positives for destructors, where this pattern is often the only correct implementation.

### The Rationale:
- Destructors are frequently called during stack unwinding after another exception has already been thrown.
- If a destructor itself throws while another exception is active, the C++ runtime immediately calls `std::terminate`.
- Therefore, to guarantee program stability, any code within a destructor that could potentially throw must be wrapped in a `try...catch` block.
- Since there's often no adequate way to recover or report an error from a destructor (for e.g. for `std::bad_alloc`), "swallowing" the exception is the standard/safest approach.

### Proposal:
Skip checks for `catch` blocks within destructors.

---
Full diff: https://github.com/llvm/llvm-project/pull/161379.diff


3 Files Affected:

- (modified) clang-tools-extra/clang-tidy/bugprone/EmptyCatchCheck.cpp (+1) 
- (modified) clang-tools-extra/docs/ReleaseNotes.rst (+4) 
- (modified) clang-tools-extra/test/clang-tidy/checkers/bugprone/empty-catch.cpp (+9) 


``````````diff
diff --git a/clang-tools-extra/clang-tidy/bugprone/EmptyCatchCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/EmptyCatchCheck.cpp
index eebab847d1070..48dc3bdfdf49e 100644
--- a/clang-tools-extra/clang-tidy/bugprone/EmptyCatchCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/EmptyCatchCheck.cpp
@@ -90,6 +90,7 @@ void EmptyCatchCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
       cxxCatchStmt(unless(isExpansionInSystemHeader()), unless(isInMacro()),
                    unless(hasCaughtType(IgnoredExceptionType)),
+                   unless(hasAncestor(cxxDestructorDecl())),
                    hasHandler(compoundStmt(
                        statementCountIs(0),
                        unless(hasAnyTextFromList(IgnoreCatchWithKeywords)))))
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index c3a6d2f9b2890..426c97225c0e1 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -244,6 +244,10 @@ Changes in existing checks
   correcting a spelling mistake on its option
   ``NamePrefixSuffixSilenceDissimilarityTreshold``.
 
+- Improved :doc:`bugprone-empty-catch
+  <clang-tidy/checks/bugprone/empty-catch>` check by allowing empty 
+  ``catch`` blocks in destructors.
+
 - Improved :doc:`bugprone-exception-escape
   <clang-tidy/checks/bugprone/exception-escape>` check's handling of lambdas:
   exceptions from captures are now diagnosed, exceptions in the bodies of
diff --git a/clang-tools-extra/test/clang-tidy/checkers/bugprone/empty-catch.cpp b/clang-tools-extra/test/clang-tidy/checkers/bugprone/empty-catch.cpp
index 8ab38229b6dbf..1319496269d86 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/bugprone/empty-catch.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone/empty-catch.cpp
@@ -65,3 +65,12 @@ void functionWithComment2() {
     // @IGNORE: relax its safe
   }
 }
+
+struct StructWithEmptyCatchInDestructor {
+  ~StructWithEmptyCatchInDestructor() {
+    try {
+    } 
+    catch (...) {
+    }
+  }
+};

``````````

</details>


https://github.com/llvm/llvm-project/pull/161379