[clang-tools-extra] b7d5577 - [clang-tidy][#51939] Exempt placement-new expressions from 'bugprone-throw-keyword-missing'

[Markus Böck via cfe-commits]

Author: Markus Böck
Date: 2021-12-15T16:59:14+01:00
New Revision: b7d55771ce3ecc5c1768bd5877dbdd312f9ab0d7

URL: https://github.com/llvm/llvm-project/commit/b7d55771ce3ecc5c1768bd5877dbdd312f9ab0d7
DIFF: https://github.com/llvm/llvm-project/commit/b7d55771ce3ecc5c1768bd5877dbdd312f9ab0d7.diff

LOG: [clang-tidy][#51939] Exempt placement-new expressions from 'bugprone-throw-keyword-missing'

The purpose of this checker is to flag a missing throw keyword, and does so by checking for the construction of an exception class that is then unused.
This works great except that placement new expressions are also flagged as those lead to the construction of an object as well, even though they are not temporary (as that is dependent on the storage).
This patch fixes the issue by exempting the match if it is within a placement-new.

Fixes https://github.com/llvm/llvm-project/issues/51939

Differential Revision: https://reviews.llvm.org/D115576

Added: 
    

Modified: 
    clang-tools-extra/clang-tidy/bugprone/ThrowKeywordMissingCheck.cpp
    clang-tools-extra/docs/ReleaseNotes.rst
    clang-tools-extra/test/clang-tidy/checkers/bugprone-throw-keyword-missing.cpp

Removed: 
    


################################################################################
diff  --git a/clang-tools-extra/clang-tidy/bugprone/ThrowKeywordMissingCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ThrowKeywordMissingCheck.cpp
index 5327a0c8d4c6b..3f5d875f471dd 100644
--- a/clang-tools-extra/clang-tidy/bugprone/ThrowKeywordMissingCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/ThrowKeywordMissingCheck.cpp
@@ -24,11 +24,13 @@ void ThrowKeywordMissingCheck::registerMatchers(MatchFinder *Finder) {
       cxxConstructExpr(
           hasType(cxxRecordDecl(
               isSameOrDerivedFrom(matchesName("[Ee]xception|EXCEPTION")))),
-          unless(anyOf(hasAncestor(stmt(
-                           anyOf(cxxThrowExpr(), callExpr(), returnStmt()))),
-                       hasAncestor(decl(anyOf(varDecl(), fieldDecl()))),
-                       allOf(hasAncestor(CtorInitializerList),
-                             unless(hasAncestor(cxxCatchStmt()))))))
+          unless(anyOf(
+              hasAncestor(
+                  stmt(anyOf(cxxThrowExpr(), callExpr(), returnStmt()))),
+              hasAncestor(decl(anyOf(varDecl(), fieldDecl()))),
+              hasAncestor(expr(cxxNewExpr(hasAnyPlacementArg(anything())))),
+              allOf(hasAncestor(CtorInitializerList),
+                    unless(hasAncestor(cxxCatchStmt()))))))
           .bind("temporary-exception-not-thrown"),
       this);
 }

diff  --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 341eb82a1e903..bcb9a0f40719c 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -148,6 +148,10 @@ Changes in existing checks
 
 - Fixed a false positive in :doc:`fuchsia-trailing-return
   <clang-tidy/checks/fuchsia-trailing-return>` for C++17 deduction guides.
+  
+- Fixed a false positive in :doc:`bugprone-throw-keyword-missing
+  <clang-tidy/checks/bugprone-throw-keyword-missing>` when creating an exception object
+  using placement new
 
 Removed checks
 ^^^^^^^^^^^^^^

diff  --git a/clang-tools-extra/test/clang-tidy/checkers/bugprone-throw-keyword-missing.cpp b/clang-tools-extra/test/clang-tidy/checkers/bugprone-throw-keyword-missing.cpp
index dff600c947070..49233c0deefdf 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/bugprone-throw-keyword-missing.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone-throw-keyword-missing.cpp
@@ -175,3 +175,14 @@ struct ExceptionRAII {
 void exceptionRAIITest() {
   ExceptionRAII E;
 }
+
+namespace std {
+typedef decltype(sizeof(void*)) size_t;
+}
+
+void* operator new(std::size_t, void*);
+
+void placeMentNewTest() {
+  alignas(RegularException) unsigned char expr[sizeof(RegularException)];
+  new (expr) RegularException{};
+}