https://bugs.gentoo.org/932579
https://github.com/boostorg/charconv/pull/183
--- a/boost/charconv/to_chars.hpp
+++ b/boost/charconv/to_chars.hpp
@@ -81,15 +81,21 @@ BOOST_CHARCONV_DECL to_chars_result to_chars(char* first, char* last, float valu
                                              chars_format fmt = chars_format::general) noexcept;
 BOOST_CHARCONV_DECL to_chars_result to_chars(char* first, char* last, double value,
                                              chars_format fmt = chars_format::general) noexcept;
+
+#ifndef BOOST_MATH_UNSUPPORTED_LONG_DOUBLE
 BOOST_CHARCONV_DECL to_chars_result to_chars(char* first, char* last, long double value,
                                              chars_format fmt = chars_format::general) noexcept;
+#endif
 
 BOOST_CHARCONV_DECL to_chars_result to_chars(char* first, char* last, float value,
                                              chars_format fmt, int precision) noexcept;
 BOOST_CHARCONV_DECL to_chars_result to_chars(char* first, char* last, double value, 
                                              chars_format fmt, int precision) noexcept;
+
+#ifndef BOOST_MATH_UNSUPPORTED_LONG_DOUBLE
 BOOST_CHARCONV_DECL to_chars_result to_chars(char* first, char* last, long double value,
                                              chars_format fmt, int precision) noexcept;
+#endif
 
 #ifdef BOOST_CHARCONV_HAS_FLOAT128
 BOOST_CHARCONV_DECL to_chars_result to_chars(char* first, char* last, __float128 value,
-- 
2.45.2