[clang] [clang][bytecode] Check __builtin_memcpy for null pointers (PR #118313)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr created 
https://github.com/llvm/llvm-project/pull/118313

None

>From 0cc2c1a52538a8fa5fe89bba77e83e00942eeaf1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbae...@redhat.com>
Date: Mon, 2 Dec 2024 16:47:50 +0100
Subject: [PATCH] [clang][bytecode] Check __builtin_memcpy for null pointers

---
 clang/lib/AST/ByteCode/InterpBuiltin.cpp      | 8 ++++++++
 clang/test/AST/ByteCode/builtin-functions.cpp | 8 ++++++++
 2 files changed, 16 insertions(+)

diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp 
b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index a217578e4936b4..de9f1f09e46405 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -1761,6 +1761,14 @@ static bool interp__builtin_memcpy(InterpState &S, 
CodePtr OpPC,
     return true;
   }
 
+  if (SrcPtr.isZero() || DestPtr.isZero()) {
+    Pointer DiagPtr = (SrcPtr.isZero() ? SrcPtr : DestPtr);
+    S.FFDiag(S.Current->getSource(OpPC), diag::note_constexpr_memcpy_null)
+        << /*IsMove=*/false << /*IsWchar=*/false << !SrcPtr.isZero()
+        << SrcPtr.toDiagnosticString(S.getASTContext());
+    return false;
+  }
+
   if (!DoBitCastPtr(S, OpPC, SrcPtr, DestPtr))
     return false;
 
diff --git a/clang/test/AST/ByteCode/builtin-functions.cpp 
b/clang/test/AST/ByteCode/builtin-functions.cpp
index 61b78e8928df4c..d38a8a7f413c52 100644
--- a/clang/test/AST/ByteCode/builtin-functions.cpp
+++ b/clang/test/AST/ByteCode/builtin-functions.cpp
@@ -1116,4 +1116,12 @@ namespace BuiltinMemcpy {
     return b;
   }
   static_assert(simple() == 12);
+
+
+  extern struct Incomplete incomplete;
+  constexpr struct Incomplete *null_incomplete = 0;
+  static_assert(__builtin_memcpy(null_incomplete, null_incomplete, 
sizeof(wchar_t))); // both-error {{not an integral constant expression}} \
+                                                                               
       // both-note {{source of 'memcpy' is nullptr}}
+
+
 }

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