[clang-tools-extra] [clang-tidy] ignore `[[clang::lifetimebound]]` param in return-const-ref-from-parameter (PR #118315)

[Congcong Cai via cfe-commits]

https://github.com/HerrCai0907 updated https://github.com/llvm/llvm-project/pull/118315

>From 82f24c9930097a1e2d2b5cb068cc5fe58cbd5cd6 Mon Sep 17 00:00:00 2001
From: Congcong Cai <congcongcai0907 at 163.com>
Date: Mon, 2 Dec 2024 23:50:12 +0800
Subject: [PATCH 1/2] [clang-tidy] ignore `[[clang::lifetimebound]]` param in
 return-const-ref-from-parameter

---
 .../ReturnConstRefFromParameterCheck.cpp      | 12 +++++++-
 clang-tools-extra/docs/ReleaseNotes.rst       |  3 +-
 .../return-const-ref-from-parameter.rst       | 28 +++++++++++++------
 .../return-const-ref-from-parameter.cpp       |  6 ++++
 4 files changed, 38 insertions(+), 11 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/bugprone/ReturnConstRefFromParameterCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ReturnConstRefFromParameterCheck.cpp
index 7da27c0474d519..1bd7abbad66d27 100644
--- a/clang-tools-extra/clang-tidy/bugprone/ReturnConstRefFromParameterCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/ReturnConstRefFromParameterCheck.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "ReturnConstRefFromParameterCheck.h"
+#include "clang/AST/Attrs.inc"
 #include "clang/AST/Expr.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
@@ -15,6 +16,14 @@ using namespace clang::ast_matchers;
 
 namespace clang::tidy::bugprone {
 
+namespace {
+
+AST_MATCHER(ParmVarDecl, hasLifetimeBoundAttr) {
+  return Node.hasAttr<LifetimeBoundAttr>();
+}
+
+} // namespace
+
 void ReturnConstRefFromParameterCheck::registerMatchers(MatchFinder *Finder) {
   const auto DRef = ignoringParens(
       declRefExpr(
@@ -22,7 +31,8 @@ void ReturnConstRefFromParameterCheck::registerMatchers(MatchFinder *Finder) {
                              qualType(lValueReferenceType(pointee(
                                           qualType(isConstQualified()))))
                                  .bind("type"))),
-                         hasDeclContext(functionDecl().bind("owner")))
+                         hasDeclContext(functionDecl().bind("owner")),
+                         unless(hasLifetimeBoundAttr()))
                  .bind("param")))
           .bind("dref"));
   const auto Func =
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 453a91e3b504cd..e00f86f7d01447 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -184,7 +184,8 @@ Changes in existing checks
   <clang-tidy/checks/bugprone/return-const-ref-from-parameter>` check to
   diagnose potential dangling references when returning a ``const &`` parameter
   by using the conditional operator ``cond ? var1 : var2`` and no longer giving
-  false positives for functions which contain lambda.
+  false positives for functions which contain lambda and ignore parameters
+  with ``[[clang::lifetimebound]]`` attribute.
   
 - Improved :doc:`bugprone-sizeof-expression
   <clang-tidy/checks/bugprone/sizeof-expression>` check to find suspicious
diff --git a/clang-tools-extra/docs/clang-tidy/checks/bugprone/return-const-ref-from-parameter.rst b/clang-tools-extra/docs/clang-tidy/checks/bugprone/return-const-ref-from-parameter.rst
index 2349e51477b7de..3e1ffd747f74a2 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/bugprone/return-const-ref-from-parameter.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/bugprone/return-const-ref-from-parameter.rst
@@ -12,15 +12,6 @@ after the call. When the function returns such a parameter also as constant refe
 then the returned reference can be used after the object it refers to has been
 destroyed.
 
-This issue can be resolved by declaring an overload of the problematic function
-where the ``const &`` parameter is instead declared as ``&&``. The developer has
-to ensure that the implementation of that function does not produce a
-use-after-free, the exact error that this check is warning against.
-Marking such an ``&&`` overload as ``deleted``, will silence the warning as 
-well. In the case of different ``const &`` parameters being returned depending
-on the control flow of the function, an overload where all problematic
-``const &`` parameters have been declared as ``&&`` will resolve the issue.
-
 Example
 -------
 
@@ -38,3 +29,22 @@ Example
 
   const S& s = fn(S{1});
   s.v; // use after free
+
+
+This issue can be resolved by declaring an overload of the problematic function
+where the ``const &`` parameter is instead declared as ``&&``. The developer has
+to ensure that the implementation of that function does not produce a
+use-after-free, the exact error that this check is warning against.
+Marking such an ``&&`` overload as ``deleted``, will silence the warning as 
+well. In the case of different ``const &`` parameters being returned depending
+on the control flow of the function, an overload where all problematic
+``const &`` parameters have been declared as ``&&`` will resolve the issue.
+
+This issue can also be resolved by adding ``[[clang::lifetimebound]]``. Clang
+enable ``-Wdangling`` warning by default which can detect mis-uses of the
+annotated function. See `lifetimebound attribute<https://clang.llvm.org/docs/AttributeReference.html#id11>`_
+for details.
+
+.. code-block:: c++
+  const int &f(const int &a [[clang::lifetimebound]]) { return a; } // no warning
+  const int &v = f(1); // warning: temporary bound to local reference 'v' will be destroyed at the end of the full-expression [-Wdangling]
diff --git a/clang-tools-extra/test/clang-tidy/checkers/bugprone/return-const-ref-from-parameter.cpp b/clang-tools-extra/test/clang-tidy/checkers/bugprone/return-const-ref-from-parameter.cpp
index 49aeb50155b157..46cb9063beda97 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/bugprone/return-const-ref-from-parameter.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone/return-const-ref-from-parameter.cpp
@@ -197,3 +197,9 @@ int const &overload_params_difference3(int p1, int const &a, int p2) { return a;
 int const &overload_params_difference3(int p1, long &&a, int p2);
 
 } // namespace overload
+
+namespace gh117696 {
+namespace use_lifetime_bound_attr {
+int const &f(int const &a [[clang::lifetimebound]]) { return a; }
+} // namespace use_lifetime_bound_attr
+} // namespace gh117696

>From 487099c3c55c407b507942c06549ada1b4b1c6ae Mon Sep 17 00:00:00 2001
From: Congcong Cai <congcongcai0907 at 163.com>
Date: Tue, 3 Dec 2024 22:04:47 +0800
Subject: [PATCH 2/2] fix format

---
 .../checks/bugprone/return-const-ref-from-parameter.rst        | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/clang-tools-extra/docs/clang-tidy/checks/bugprone/return-const-ref-from-parameter.rst b/clang-tools-extra/docs/clang-tidy/checks/bugprone/return-const-ref-from-parameter.rst
index 3e1ffd747f74a2..ba47399914de3f 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/bugprone/return-const-ref-from-parameter.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/bugprone/return-const-ref-from-parameter.rst
@@ -42,9 +42,10 @@ on the control flow of the function, an overload where all problematic
 
 This issue can also be resolved by adding ``[[clang::lifetimebound]]``. Clang
 enable ``-Wdangling`` warning by default which can detect mis-uses of the
-annotated function. See `lifetimebound attribute<https://clang.llvm.org/docs/AttributeReference.html#id11>`_
+annotated function. See `lifetimebound attribute <https://clang.llvm.org/docs/AttributeReference.html#id11>`_
 for details.
 
 .. code-block:: c++
+
   const int &f(const int &a [[clang::lifetimebound]]) { return a; } // no warning
   const int &v = f(1); // warning: temporary bound to local reference 'v' will be destroyed at the end of the full-expression [-Wdangling]