[clang] [clang][bytecode] Check strlen impl for primitive arrays (PR #157494)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr created https://github.com/llvm/llvm-project/pull/157494

Fixes #157428

>From 720cbfe0b715c6a2f1c02631b96dc560fedab88b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Mon, 8 Sep 2025 17:36:52 +0200
Subject: [PATCH] [clang][bytecode] Check strlen impl for primitive arrays

---
 clang/lib/AST/ByteCode/InterpBuiltin.cpp |  3 +++
 clang/test/AST/ByteCode/builtins.c       | 19 +++++++++++++++++++
 2 files changed, 22 insertions(+)
 create mode 100644 clang/test/AST/ByteCode/builtins.c

diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index a0dcdace854b9..1739aa3e4c1d4 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -300,6 +300,9 @@ static bool interp__builtin_strlen(InterpState &S, CodePtr OpPC,
   if (!CheckDummy(S, OpPC, StrPtr.block(), AK_Read))
     return false;
 
+  if (!StrPtr.getFieldDesc()->isPrimitiveArray())
+    return false;
+
   assert(StrPtr.getFieldDesc()->isPrimitiveArray());
   unsigned ElemSize = StrPtr.getFieldDesc()->getElemSize();
 
diff --git a/clang/test/AST/ByteCode/builtins.c b/clang/test/AST/ByteCode/builtins.c
new file mode 100644
index 0000000000000..a51260cd3431f
--- /dev/null
+++ b/clang/test/AST/ByteCode/builtins.c
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -fexperimental-new-constant-interpreter %s -verify
+// RUN: %clang_cc1                                         %s -verify=ref
+
+// expected-no-diagnostics
+// ref-no-diagnostics
+
+extern __SIZE_TYPE__ strlen(const char *);
+
+struct str_t {
+  char s1[sizeof("a")];
+};
+static const struct str_t str1 = {"a"};
+#define str ((const char *)&str1)
+int structStrlen(void) {
+  if (strlen(str) == 1)
+    return 0;
+  return 1;
+}
+