From de42f13712cbd6476a252a0cb9e25feb8122ba4d Mon Sep 17 00:00:00 2001
From: Alexey Ochapov <alexez@alexez.com>
Date: Tue, 15 Dec 2020 04:48:34 +0300
Subject: [PATCH] use `is_constant_evaluated()`` to initialize class `value`
 with string

---
 include/fmt/core.h   | 15 ++++++++++++++-
 include/fmt/format.h |  8 --------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/include/fmt/core.h b/include/fmt/core.h
index e7204be5..e2db21af 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -283,6 +283,14 @@ struct monostate {};
 
 namespace detail {
 
+constexpr bool is_constant_evaluated() FMT_DETECTED_NOEXCEPT {
+#ifdef __cpp_lib_is_constant_evaluated
+  return std::is_constant_evaluated();
+#else
+  return false;
+#endif
+}
+
 // A helper function to suppress "conditional expression is constant" warnings.
 template <typename T> constexpr T const_check(T value) { return value; }
 
@@ -1082,7 +1090,12 @@ template <typename Context> class value {
   FMT_INLINE value(long double val) : long_double_value(val) {}
   constexpr FMT_INLINE value(bool val) : bool_value(val) {}
   constexpr FMT_INLINE value(char_type val) : char_value(val) {}
-  FMT_CONSTEXPR value(const char_type* val) : string() { string.data = val; }
+  FMT_CONSTEXPR value(const char_type* val) {
+    string.data = val;
+    if (is_constant_evaluated()) {
+      string.size = {};
+    }
+  }
   FMT_CONSTEXPR value(basic_string_view<char_type> val) {
     string.data = val.data();
     string.size = val.size();
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 09f2d782..774d5a4b 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -288,14 +288,6 @@ namespace detail {
 #  define FMT_CONSTEXPR20 inline
 #endif
 
-constexpr bool is_constant_evaluated() FMT_DETECTED_NOEXCEPT {
-#ifdef __cpp_lib_is_constant_evaluated
-  return std::is_constant_evaluated();
-#else
-  return false;
-#endif
-}
-
 // An equivalent of `*reinterpret_cast<Dest*>(&source)` that doesn't have
 // undefined behavior (e.g. due to type aliasing).
 // Example: uint64_t d = bit_cast<uint64_t>(2.718);