[clang] [clang] Create PointerToBoolean casts for C casts (PR #155368)

[Timm Baeder via cfe-commits]

Timm =?utf-8?q?Bäder?= <tbaeder at redhat.com>,
Timm =?utf-8?q?Bäder?= <tbaeder at redhat.com>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/155368 at github.com>


https://github.com/tbaederr updated https://github.com/llvm/llvm-project/pull/155368

>From cfe28648d256469e871e79fe44bad7eb1819aaa2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Tue, 26 Aug 2025 09:38:44 +0200
Subject: [PATCH 1/3] [clang] Create PointerToBoolean casts for C casts

Don't create CK_BitCast casts from `nullptr_t` to `bool`.

Fixes #155126
---
 clang/lib/Sema/SemaCast.cpp      |  7 ++++++-
 clang/test/CodeGen/issue155126.c | 11 +++++++++++
 clang/test/Sema/constexpr.c      |  2 ++
 3 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/CodeGen/issue155126.c

diff --git a/clang/lib/Sema/SemaCast.cpp b/clang/lib/Sema/SemaCast.cpp
index de22419ee35de..9727a15aabc72 100644
--- a/clang/lib/Sema/SemaCast.cpp
+++ b/clang/lib/Sema/SemaCast.cpp
@@ -3170,7 +3170,12 @@ void CastOperation::CheckCStyleCast() {
       SrcExpr = ExprError();
       return;
     }
-    if (!DestType->isNullPtrType()) {
+    if (DestType->isBooleanType()) {
+      SrcExpr = ImplicitCastExpr::Create(
+          Self.Context, DestType, CK_PointerToBoolean, SrcExpr.get(), nullptr,
+          VK_PRValue, Self.CurFPFeatureOverrides());
+
+    } else if (!DestType->isNullPtrType()) {
       // Implicitly cast from the null pointer type to the type of the
       // destination.
       CastKind CK = DestType->isPointerType() ? CK_NullToPointer : CK_BitCast;
diff --git a/clang/test/CodeGen/issue155126.c b/clang/test/CodeGen/issue155126.c
new file mode 100644
index 0000000000000..ec15355d8d7df
--- /dev/null
+++ b/clang/test/CodeGen/issue155126.c
@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 -std=c23 -verify %s
+// RUN: %clang_cc1 -std=c23 -verify -fexperimental-new-constant-interpreter %s
+
+// expected-no-diagnostics
+
+enum e : bool { b = true };
+void foo ()
+{
+  enum e e1;
+  e1 = (bool) nullptr;
+}
diff --git a/clang/test/Sema/constexpr.c b/clang/test/Sema/constexpr.c
index 3dcb0b3a7d95f..e8f0700c5894f 100644
--- a/clang/test/Sema/constexpr.c
+++ b/clang/test/Sema/constexpr.c
@@ -391,3 +391,5 @@ void ghissue109095() {
   _Static_assert(i == c[0]); // expected-error {{static assertion expression is not an integral constant expression}}\
                              // expected-note {{initializer of 'i' is not a constant expression}}
 }
+constexpr bool b2 = (bool)nullptr;
+_Static_assert(!b2);

>From 8ce7ded176a4280fe89235ce7f170039ade524ab Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Tue, 26 Aug 2025 12:04:46 +0200
Subject: [PATCH 2/3] Actually emit code

---
 clang/test/CodeGen/issue155126.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/clang/test/CodeGen/issue155126.c b/clang/test/CodeGen/issue155126.c
index ec15355d8d7df..f071d36799dce 100644
--- a/clang/test/CodeGen/issue155126.c
+++ b/clang/test/CodeGen/issue155126.c
@@ -1,7 +1,5 @@
-// RUN: %clang_cc1 -std=c23 -verify %s
-// RUN: %clang_cc1 -std=c23 -verify -fexperimental-new-constant-interpreter %s
-
-// expected-no-diagnostics
+// RUN: %clang_cc1 -std=c23 %s -emit-llvm -o -
+// RUN: %clang_cc1 -std=c23 %s -emit-llvm -o - -fexperimental-new-constant-interpreter
 
 enum e : bool { b = true };
 void foo ()

>From 9fe5195cd72529b705a735537713541e3ec175da Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Tue, 26 Aug 2025 17:45:24 +0200
Subject: [PATCH 3/3] Add FileCheck output

---
 clang/test/CodeGen/issue155126.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/clang/test/CodeGen/issue155126.c b/clang/test/CodeGen/issue155126.c
index f071d36799dce..618772a42984a 100644
--- a/clang/test/CodeGen/issue155126.c
+++ b/clang/test/CodeGen/issue155126.c
@@ -1,7 +1,15 @@
-// RUN: %clang_cc1 -std=c23 %s -emit-llvm -o -
-// RUN: %clang_cc1 -std=c23 %s -emit-llvm -o - -fexperimental-new-constant-interpreter
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 5
+// RUN: %clang_cc1 -std=c23 %s -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -std=c23 %s -emit-llvm -o - -fexperimental-new-constant-interpreter | FileCheck %s
 
 enum e : bool { b = true };
+// CHECK-LABEL: define dso_local void @foo(
+// CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[E1:%.*]] = alloca i8, align 1
+// CHECK-NEXT:    store i8 0, ptr [[E1]], align 1
+// CHECK-NEXT:    ret void
+//
 void foo ()
 {
   enum e e1;