From ea32e86deed6e8a8cd6116dc275e358a901d2b50 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@nuwen.net>
Date: Wed, 15 Jun 2022 18:35:17 -0700
Subject: [PATCH] Mark constants as `_INLINE_VAR constexpr`. (#2792)

---
 stl/inc/functional |  2 +-
 stl/inc/regex      | 16 ++++++++--------
 stl/inc/vector     |  5 +++--
 stl/inc/xstring    |  3 ++-
 4 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/stl/inc/functional b/stl/inc/functional
index 783433cd1..b3c0b8bed 100644
--- a/stl/inc/functional
+++ b/stl/inc/functional
@@ -722,7 +722,7 @@ private:
     virtual const void* _Get() const noexcept = 0;
 };
 
-constexpr size_t _Space_size = (_Small_object_num_ptrs - 1) * sizeof(void*);
+_INLINE_VAR constexpr size_t _Space_size = (_Small_object_num_ptrs - 1) * sizeof(void*);
 
 template <class _Impl> // determine whether _Impl must be dynamically allocated
 _INLINE_VAR constexpr bool _Is_large = sizeof(_Impl) > _Space_size || alignof(_Impl) > alignof(max_align_t)
diff --git a/stl/inc/regex b/stl/inc/regex
index b13d30b97..d84142b14 100644
--- a/stl/inc/regex
+++ b/stl/inc/regex
@@ -1155,16 +1155,16 @@ _NODISCARD bool operator!=(const match_results<_BidIt, _Alloc>& _Left, const mat
 }
 #endif // !_HAS_CXX20
 
-const unsigned int _BRE_MAX_GRP = 9U;
+_INLINE_VAR constexpr unsigned int _BRE_MAX_GRP = 9U;
 
-const unsigned int _Bmp_max   = 256U; // must fit in an unsigned int
-const unsigned int _Bmp_shift = 3U;
-const unsigned int _Bmp_chrs  = 1U << _Bmp_shift; // # of bits to be stored in each char
-const unsigned int _Bmp_mask  = _Bmp_chrs - 1U;
-const unsigned int _Bmp_size  = (_Bmp_max + _Bmp_chrs - 1U) / _Bmp_chrs;
+_INLINE_VAR constexpr unsigned int _Bmp_max   = 256U; // must fit in an unsigned int
+_INLINE_VAR constexpr unsigned int _Bmp_shift = 3U;
+_INLINE_VAR constexpr unsigned int _Bmp_chrs  = 1U << _Bmp_shift; // # of bits to be stored in each char
+_INLINE_VAR constexpr unsigned int _Bmp_mask  = _Bmp_chrs - 1U;
+_INLINE_VAR constexpr unsigned int _Bmp_size  = (_Bmp_max + _Bmp_chrs - 1U) / _Bmp_chrs;
 
-const unsigned int _Buf_incr        = 16U;
-const unsigned int _ARRAY_THRESHOLD = 4U;
+_INLINE_VAR constexpr unsigned int _Buf_incr        = 16U;
+_INLINE_VAR constexpr unsigned int _ARRAY_THRESHOLD = 4U;
 
 enum _Node_flags : int { // flags for nfa nodes with special properties
     _Fl_none    = 0x00,
diff --git a/stl/inc/vector b/stl/inc/vector
index d9d70aca7..de2e3a19c 100644
--- a/stl/inc/vector
+++ b/stl/inc/vector
@@ -2108,8 +2108,9 @@ vector(_Iter, _Iter, _Alloc = _Alloc()) -> vector<_Iter_value_t<_Iter>, _Alloc>;
 template <class _Alloc>
 class vector<bool, _Alloc>;
 
-using _Vbase         = unsigned int; // word type for vector<bool> representation
-constexpr int _VBITS = 8 * sizeof(_Vbase); // at least CHAR_BITS bits per word
+using _Vbase = unsigned int; // word type for vector<bool> representation
+
+_INLINE_VAR constexpr int _VBITS = 8 * sizeof(_Vbase); // at least CHAR_BITS bits per word
 
 template <class _Ty, class _Alloc>
 _NODISCARD _CONSTEXPR20 bool operator==(const vector<_Ty, _Alloc>& _Left, const vector<_Ty, _Alloc>& _Right) {
diff --git a/stl/inc/xstring b/stl/inc/xstring
index 395ec12ae..ff946f56a 100644
--- a/stl/inc/xstring
+++ b/stl/inc/xstring
@@ -2324,8 +2324,9 @@ public:
     size_type _Myres  = 0; // current storage reserved for string
 };
 
+// get _Ty's size after being EBCO'd
 template <class _Ty>
-constexpr size_t _Size_after_ebco_v = is_empty_v<_Ty> ? 0 : sizeof(_Ty); // get _Ty's size after being EBCO'd
+_INLINE_VAR constexpr size_t _Size_after_ebco_v = is_empty_v<_Ty> ? 0 : sizeof(_Ty);
 
 struct _String_constructor_concat_tag {
     // tag to select constructors used by basic_string's concatenation operators (operator+)