From 5ac1dd41aabbaff89109383933301cfc1dd495b4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B3n=20Bjarni=20Bjarnason?= <jbbjarnason@gmail.com>
Date: Fri, 13 Oct 2023 09:40:30 +0000
Subject: [PATCH] generating right sized constexpr string_view of unit_symbol

---
 src/core/include/mp-units/unit.h | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/src/core/include/mp-units/unit.h b/src/core/include/mp-units/unit.h
index f381d3701..b5163195b 100644
--- a/src/core/include/mp-units/unit.h
+++ b/src/core/include/mp-units/unit.h
@@ -819,19 +819,17 @@ template<typename CharT = char, Unit U>
 
 template<typename CharT, Unit U, unit_symbol_formatting fmt>
 struct const_unit_symbol {
-  static constexpr std::size_t size{255};
+  static consteval auto unit_symbol_len() -> std::size_t { return unit_symbol(U{}, fmt).size(); }
   static constexpr auto impl() noexcept
   {
-    std::array<CharT, size> array{};
-    auto out_it{mp_units::unit_symbol_to(array.begin(), U{}, fmt)};
-    auto len = std::distance(array.begin(), out_it);
-    return std::make_pair(array, len);
+    std::array<CharT, unit_symbol_len() + 1> buffer{};
+    mp_units::unit_symbol_to(std::begin(buffer), U{}, fmt);
+    return buffer;
   }
   // Give the joined string static storage
   static constexpr auto arr = impl();
-  static_assert(arr.second < size);
   // View as a std::string_view
-  static constexpr std::basic_string_view<CharT> value{arr.first.data(), arr.second};
+  static constexpr std::basic_string_view<CharT> value{arr.data(), arr.size() - 1};
 };
 
 template<typename CharT = char, Unit U, unit_symbol_formatting fmt = unit_symbol_formatting{}>