Throw on truncation for the precision value in the floating point formatter

1 files changed, 15 insertions, 2 deletions

diff --git a/include/cxxformat/formatters.hpp b/include/cxxformat/formatters.hpp
index c32d2e8..b248b17 100644
--- a/include/cxxformat/formatters.hpp
+++ b/include/cxxformat/formatters.hpp
@@ -312,12 +312,25 @@ namespace format {
 					assert(!"Unsupported conversion; should have been caught by formatter<T>::conversionSupported");
 			}
 
+			optional_int<int> intPrecision;
+
+			if (precision)
+			{
+				const auto val = *precision;
+				constexpr auto max = std::numeric_limits<int>::max();
+				if (val > max)
+				{
+					throw std::out_of_range{"Precision is too big; maximum supported for floating point types is " + std::to_string(max)};
+				}
+				intPrecision = static_cast<int>(val);
+			}
+
 			char* data, *end;
 			std::errc ec;
-			const auto call_to_chars = [format, precision, t, &data, &end, &ec](char* data_, std::size_t size)
+			const auto call_to_chars = [format, intPrecision, t, &data, &end, &ec](char* data_, std::size_t size)
 			{
 				data = data_;
-				const auto [end_, ec_] = precision ? std::to_chars(data, data + size, t, format, *precision) : std::to_chars(data, data + size, t, format);
+				const auto [end_, ec_] = intPrecision ? std::to_chars(data, data + size, t, format, *intPrecision) : std::to_chars(data, data + size, t, format);
 				end = end_;
 				ec = ec_;
 			};