https://github.com/tbaederr updated
https://github.com/llvm/llvm-project/pull/116999
>From c9c39e81e3fae1351691feaf99528997114810cb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbae...@redhat.com>
Date: Wed, 20 Nov 2024 17:14:01 +0100
Subject: [PATCH] [clang][bytecode] Fix bitcasting from null pointers
This looks a little ugly now, I should wait for #116843.
---
clang/lib/AST/ByteCode/InterpBuiltinBitCast.cpp | 10 +++++++---
clang/test/AST/ByteCode/builtin-bit-cast.cpp | 6 ++++++
2 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/clang/lib/AST/ByteCode/InterpBuiltinBitCast.cpp
b/clang/lib/AST/ByteCode/InterpBuiltinBitCast.cpp
index 03c556cd70bb7a..6ee3826fb3eea6 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltinBitCast.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltinBitCast.cpp
@@ -254,9 +254,13 @@ static bool readPointerToBuffer(const Context &Ctx, const
Pointer &FromPtr,
}
assert(P.isInitialized());
- // nullptr_t is a PT_Ptr for us, but it's still not std::is_pointer_v.
- if (T == PT_Ptr)
- assert(false && "Implement casting to pointer types");
+ if (T == PT_Ptr) {
+ assert(P.getType()->isNullPtrType());
+ // Clang treats nullptr_t has having NO bits in its value
+ // representation. So, we accept it here and leave its bits
+ // uninitialized.
+ return true;
+ }
auto Buff =
std::make_unique<std::byte[]>(ObjectReprChars.getQuantity());
diff --git a/clang/test/AST/ByteCode/builtin-bit-cast.cpp
b/clang/test/AST/ByteCode/builtin-bit-cast.cpp
index d3935b4f921b3f..f89eb3584bbcff 100644
--- a/clang/test/AST/ByteCode/builtin-bit-cast.cpp
+++ b/clang/test/AST/ByteCode/builtin-bit-cast.cpp
@@ -133,8 +133,14 @@ namespace simple {
/// This works in GCC and in the bytecode interpreter, but the current
interpreter
/// diagnoses it.
+ /// FIXME: Should also be rejected in the bytecode interpreter.
static_assert(__builtin_bit_cast(intptr_t, nullptr) == 0); // ref-error
{{not an integral constant expression}} \
// ref-note
{{indeterminate value can only initialize an object}}
+
+ constexpr int test_from_nullptr_pass = (__builtin_bit_cast(unsigned
char[sizeof(nullptr)], nullptr), 0);
+ constexpr unsigned char NPData[sizeof(nullptr)] = {1,2,3,4};
+ constexpr nullptr_t NP = __builtin_bit_cast(nullptr_t, NPData);
+ static_assert(NP == nullptr);
}
namespace Fail {
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