[clang] [clang][Sema] Fix type of an statement expression ending with an atomic type (PR #119711)

[Alejandro Álvarez Ayllón via cfe-commits]

https://github.com/alejandro-alvarez-sonarsource updated https://github.com/llvm/llvm-project/pull/119711

>From d398fa13c2fa141954c79ca68a59c6ac506b393f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alejandro=20=C3=81lvarez=20Ayll=C3=B3n?=
 <alejandro.alvarez at sonarsource.com>
Date: Wed, 11 Dec 2024 15:43:58 +0100
Subject: [PATCH 1/4] Add regression test

---
 clang/test/Sema/gh106576.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
 create mode 100644 clang/test/Sema/gh106576.c

diff --git a/clang/test/Sema/gh106576.c b/clang/test/Sema/gh106576.c
new file mode 100644
index 00000000000000..792977dea14132
--- /dev/null
+++ b/clang/test/Sema/gh106576.c
@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+typedef _Atomic char atomic_char;
+
+typedef _Atomic char atomic_char;
+
+atomic_char counter;
+
+char load_plus_one(void) {
+  return ({counter;}) + 1; // no crash
+}
+
+char type_of_stmt_expr(void) {
+  typeof(({counter;})) y = ""; // expected-error-re {{incompatible pointer to integer conversion initializing 'typeof (({{{.*}}}))' (aka 'char') with an expression of type 'char[1]'}}
+  return y;
+}

>From 296aa35fe32449067c69d2b40031af0dd6822a07 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alejandro=20=C3=81lvarez=20Ayll=C3=B3n?=
 <alejandro.alvarez at sonarsource.com>
Date: Thu, 12 Dec 2024 15:08:56 +0100
Subject: [PATCH 2/4] Tentative fix

---
 clang/lib/Sema/SemaExpr.cpp | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 20bf6f7f6f28ff..165447efb345c5 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -15861,10 +15861,19 @@ ExprResult Sema::ActOnStmtExprResult(ExprResult ER) {
   if (Cast && Cast->getCastKind() == CK_ARCConsumeObject)
     return Cast->getSubExpr();
 
+  auto Ty = E->getType().getUnqualifiedType();
+
+  // If the type is an atomic, the statement type is the underlying type.
+  if (const AtomicType *AT = Ty->getAs<AtomicType>()) {
+    Ty = AT->getValueType().getUnqualifiedType();
+    return ImplicitCastExpr::Create(Context, Ty, CK_AtomicToNonAtomic, E,
+                                    /*base path*/ nullptr, VK_PRValue,
+                                    FPOptionsOverride());
+  }
+
   // FIXME: Provide a better location for the initialization.
   return PerformCopyInitialization(
-      InitializedEntity::InitializeStmtExprResult(
-          E->getBeginLoc(), E->getType().getUnqualifiedType()),
+      InitializedEntity::InitializeStmtExprResult(E->getBeginLoc(), Ty),
       SourceLocation(), E);
 }
 

>From d13e1090c641314aae8eef50f1b0fb5c0ec67e39 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alejandro=20=C3=81lvarez=20Ayll=C3=B3n?=
 <alejandro.alvarez at sonarsource.com>
Date: Thu, 12 Dec 2024 15:30:07 +0100
Subject: [PATCH 3/4] Use PerformImplicitConversion

---
 clang/lib/Sema/SemaExpr.cpp | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 165447efb345c5..45ae97807c2032 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -15866,9 +15866,7 @@ ExprResult Sema::ActOnStmtExprResult(ExprResult ER) {
   // If the type is an atomic, the statement type is the underlying type.
   if (const AtomicType *AT = Ty->getAs<AtomicType>()) {
     Ty = AT->getValueType().getUnqualifiedType();
-    return ImplicitCastExpr::Create(Context, Ty, CK_AtomicToNonAtomic, E,
-                                    /*base path*/ nullptr, VK_PRValue,
-                                    FPOptionsOverride());
+    return PerformImplicitConversion(E, Ty, AssignmentAction::Casting);
   }
 
   // FIXME: Provide a better location for the initialization.

>From 02d8385cc0f824ff0436a7b0a42d16555e5ee0c5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alejandro=20=C3=81lvarez=20Ayll=C3=B3n?=
 <alejandro.alvarez at sonarsource.com>
Date: Wed, 18 Dec 2024 09:19:51 +0100
Subject: [PATCH 4/4] Add release note

---
 clang/docs/ReleaseNotes.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 408b2800f9e79c..24420d9dd49d5e 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -853,6 +853,7 @@ Bug Fixes to AST Handling
 - Clang now uses the location of the begin of the member expression for ``CallExpr``
   involving deduced ``this``. (#GH116928)
 - Fixed printout of AST that uses pack indexing expression. (#GH116486)
+- Fixed type deduction of an statement expression (a GCC extension) ending with an atomic type. (#GH106576)
 
 Miscellaneous Bug Fixes
 ^^^^^^^^^^^^^^^^^^^^^^^