[libcxx-commits] [libcxx] [libc++] Remove potential 0-sized array in __compressed_pair_padding (PR #109028)

[via libcxx-commits]

https://github.com/serge-sans-paille updated https://github.com/llvm/llvm-project/pull/109028

>From 312cb4e31473fca528f9ad797aa52b6576e39388 Mon Sep 17 00:00:00 2001
From: serge-sans-paille <sguelton at mozilla.com>
Date: Wed, 18 Sep 2024 11:25:18 +0200
Subject: [PATCH 1/2] [libc++] Remove potential 0-sized array in
 __packed_format_arg_store

---
 libcxx/include/__format/format_arg_store.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libcxx/include/__format/format_arg_store.h b/libcxx/include/__format/format_arg_store.h
index 68e936acecade7..9a4a41df6d4e68 100644
--- a/libcxx/include/__format/format_arg_store.h
+++ b/libcxx/include/__format/format_arg_store.h
@@ -234,6 +234,11 @@ struct __packed_format_arg_store {
   uint64_t __types_ = 0;
 };
 
+template <class _Context>
+struct __packed_format_arg_store<_Context, 0> {
+  uint64_t __types_ = 0;
+};
+
 template <class _Context, size_t _Np>
 struct __unpacked_format_arg_store {
   basic_format_arg<_Context> __args_[_Np];

>From 87b87bda38b3cf4f01483a75ff536757c5b9c38f Mon Sep 17 00:00:00 2001
From: serge-sans-paille <sguelton at mozilla.com>
Date: Mon, 30 Sep 2024 10:49:25 +0200
Subject: [PATCH 2/2] [libc++] Remove potential 0-sized array in
 __compressed_pair_padding

---
 libcxx/include/__memory/compressed_pair.h | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/libcxx/include/__memory/compressed_pair.h b/libcxx/include/__memory/compressed_pair.h
index 629e3ad8848ffa..a612c093e429dd 100644
--- a/libcxx/include/__memory/compressed_pair.h
+++ b/libcxx/include/__memory/compressed_pair.h
@@ -52,13 +52,17 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 #ifndef _LIBCPP_ABI_NO_COMPRESSED_PAIR_PADDING
 
-template <class _ToPad>
+template <class _ToPad,
+          size_t N = ((is_empty<_ToPad>::value && !__libcpp_is_final<_ToPad>::value) || is_reference<_ToPad>::value)
+                       ? 0
+                       : sizeof(_ToPad) - __datasizeof_v<_ToPad>>
 class __compressed_pair_padding {
-  char __padding_[((is_empty<_ToPad>::value && !__libcpp_is_final<_ToPad>::value) || is_reference<_ToPad>::value)
-                      ? 0
-                      : sizeof(_ToPad) - __datasizeof_v<_ToPad>];
+  char __padding_[N];
 };
 
+template <class _ToPad>
+class __compressed_pair_padding<_ToPad, 0> {};
+
 #  define _LIBCPP_COMPRESSED_PAIR(T1, Initializer1, T2, Initializer2)                                                  \
     _LIBCPP_NO_UNIQUE_ADDRESS __attribute__((__aligned__(_LIBCPP_ALIGNOF(T2)))) T1 Initializer1;                       \
     _LIBCPP_NO_UNIQUE_ADDRESS ::std::__compressed_pair_padding<T1> _LIBCPP_CONCAT3(__padding1_, __LINE__, _);          \