[libcxx-commits] [libcxx] [libc++] P3391R2: `constexpr` integral overloads of `to_(w)string` (PR #205025)

[Timothy Herchen via libcxx-commits]

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@@ -3774,12 +3780,41 @@ stoull(const string& __str, size_t* __idx = nullptr, int __base = 10);
 [[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI double stod(const string& __str, size_t* __idx = nullptr);
 [[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI long double stold(const string& __str, size_t* __idx = nullptr);
 
+#  if _LIBCPP_STD_VER >= 26
+
+template <class _String, class _Integer>
+constexpr _String __integer_to_string(_Integer __val) {
+  // numeric_limits::digits10 returns value less on 1 than desired for unsigned numbers.
+  // For example, for 1-byte unsigned value digits10 is 2 (999 can not be represented), so we need +1 here.
+  constexpr size_t __buf_size = numeric_limits<_Integer>::digits10 + 2; // +1 for minus, +1 for digits10
+  char __buf[__buf_size];
+  const auto [__ptr, __ec] = std::to_chars(__buf, __buf + __buf_size, __val);
+  _LIBCPP_ASSERT_INTERNAL(__ec == errc(), "__buf_size must be large enough to accomodate the value");
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anematode wrote:

accommodate

https://github.com/llvm/llvm-project/pull/205025