Suppress GCC-12+ warning of too big a memset

Author: mborland

include/boost/decimal/charconv.hpp

@@ -586,8 +586,28 @@ BOOST_DECIMAL_CONSTEXPR auto to_chars_fixed_impl(char* first, char* last, const
             // We can skip the rest if there's nothing more to do for the required precision
             if (significand == 0)
             {
-                std::memset(first, '0', static_cast<std::size_t>(precision - num_leading_zeros));
-                return {first + precision, std::errc()};
+                if (precision - num_leading_zeros > 0)
+                {
+                    #if defined(__GNUC__) && __GNUC__ >= 12
+                    #pragma GCC diagnostic push
+                    #pragma GCC diagnostic ignored "-Warray-bounds"
+                    #endif
+
+                    // We have already done the check to make sure that casting this to size_t does not cause
+                    // unsigned rollover so we ignore GCC-12+ warning us about using memset on a huge number
+                    // We have also previously checked the buffer size
+                    std::memset(first, '0', static_cast<std::size_t>(precision - num_leading_zeros));
+
+                    #if defined(__GNUC__) && __GNUC__ >= 12
+                    #pragma GCC diagnostic pop
+                    #endif
+
+                    return {first + precision, std::errc()};
+                }
+                else
+                {
+                    return {first, std::errc()};
+                }
             }
         }
     }