[clang-tools-extra] [clang-tidy] fix bugprone-sizeof-expression when sizeof expression with template types (PR #115275)

[Congcong Cai via cfe-commits]

https://github.com/HerrCai0907 created 
https://github.com/llvm/llvm-project/pull/115275

Fixed: #115175.
`dependent type` are not the same even pointers are the same.


>From 06fb72b3720e3c457fc672c38258474879006682 Mon Sep 17 00:00:00 2001
From: Congcong Cai <congcongcai0...@163.com>
Date: Thu, 7 Nov 2024 15:21:48 +0800
Subject: [PATCH] [clang-tidy] fix bugprone-sizeof-expression when sizeof
 expression with template types

Fixed: #115175.
`dependent type` are not the same even pointers are the same.
---
 .../clang-tidy/bugprone/SizeofExpressionCheck.cpp            | 4 +++-
 clang-tools-extra/docs/ReleaseNotes.rst                      | 3 ++-
 .../test/clang-tidy/checkers/bugprone/sizeof-expression.cpp  | 5 +++++
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.cpp 
b/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.cpp
index 628d30ce7f73fe..7269683384f6b5 100644
--- a/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.cpp
@@ -400,7 +400,9 @@ void SizeofExpressionCheck::check(const 
MatchFinder::MatchResult &Result) {
            "suspicious usage of 'sizeof(array)/sizeof(...)';"
            " denominator differs from the size of array elements")
           << E->getLHS()->getSourceRange() << E->getRHS()->getSourceRange();
-    } else if (NumTy && DenomTy && NumTy == DenomTy) {
+    } else if (NumTy && DenomTy && NumTy == DenomTy &&
+               !NumTy->isDependentType()) {
+      // dependent type should not be compared.
       diag(E->getOperatorLoc(),
            "suspicious usage of 'sizeof(...)/sizeof(...)'; both expressions "
            "have the same type")
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst 
b/clang-tools-extra/docs/ReleaseNotes.rst
index abcdcc25705bf5..4fa8292ff89745 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -175,7 +175,8 @@ Changes in existing checks
 - Improved :doc:`bugprone-sizeof-expression
   <clang-tidy/checks/bugprone/sizeof-expression>` check to find suspicious
   usages of ``sizeof()``, ``alignof()``, and ``offsetof()`` when adding or
-  subtracting from a pointer directly or when used to scale a numeric value.
+  subtracting from a pointer directly or when used to scale a numeric value and
+  fix false positive when sizeof expression with template types.
 
 - Improved :doc:`bugprone-unchecked-optional-access
   <clang-tidy/checks/bugprone/unchecked-optional-access>` to support
diff --git 
a/clang-tools-extra/test/clang-tidy/checkers/bugprone/sizeof-expression.cpp 
b/clang-tools-extra/test/clang-tidy/checkers/bugprone/sizeof-expression.cpp
index 81efd87345c97e..f3ab78c7355b28 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/bugprone/sizeof-expression.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone/sizeof-expression.cpp
@@ -385,3 +385,8 @@ int ValidExpressions() {
   sum += sizeof(PtrArray) / sizeof(A[0]);
   return sum;
 }
+
+template<class T>
+int ValidateTemplateTypeExpressions(T t) {
+  return sizeof(t.val) / sizeof(t.val[0]);
+}

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