Fix calculation of max buffer length not accounting for negative signs

boostorg · Apr 18, 2024 · 2ba5773 · 2ba5773
1 parent cfbf18f
commit 2ba5773
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Showing 3 changed files with 5 additions and 4 deletions.
diff --git a/fuzzing/old_crashes/to_chars_int/crash-4b0b4ca7b862f00f7cd4c015af733b8ff83b4357 b/fuzzing/old_crashes/to_chars_int/crash-4b0b4ca7b862f00f7cd4c015af733b8ff83b4357
diff --git a/fuzzing/old_crashes/to_chars_int/crash-bd2f2ecb3cea66ed93a8e24d4e14913486ff8eaf b/fuzzing/old_crashes/to_chars_int/crash-bd2f2ecb3cea66ed93a8e24d4e14913486ff8eaf
diff --git a/include/boost/charconv/detail/to_chars_integer_impl.hpp b/include/boost/charconv/detail/to_chars_integer_impl.hpp
@@ -89,8 +89,7 @@ BOOST_CHARCONV_CONSTEXPR to_chars_result to_chars_integer_impl(char* first, char
 
     char buffer[10] {};
     int converted_value_digits {};
-    const std::ptrdiff_t user_buffer_size = last - first;
-    BOOST_ATTRIBUTE_UNUSED bool is_negative = false;
+    bool is_negative = false;
 
     if (first > last)
     {
@@ -115,6 +114,8 @@ BOOST_CHARCONV_CONSTEXPR to_chars_result to_chars_integer_impl(char* first, char
         unsigned_value = static_cast<Unsigned_Integer>(value);
     }
 
+    const std::ptrdiff_t user_buffer_size = last - first - static_cast<std::ptrdiff_t>(is_negative);
+
     // If the type is less than 32 bits we can use this without change
     // If the type is greater than 32 bits we use a binary search tree to figure out how many digits
     // are present and then decompose the value into two (or more) std::uint32_t of known length so that we
@@ -314,8 +315,6 @@ BOOST_CHARCONV_CONSTEXPR to_chars_result to_chars_128integer_impl(char* first, c
 template <typename Integer, typename Unsigned_Integer>
 BOOST_CHARCONV_CONSTEXPR to_chars_result to_chars_integer_impl(char* first, char* last, Integer value, int base) noexcept
 {
-    const std::ptrdiff_t output_length = last - first;
-
     if (!((first <= last) && (base >= 2 && base <= 36)))
     {
         return {last, std::errc::invalid_argument};
@@ -347,6 +346,8 @@ BOOST_CHARCONV_CONSTEXPR to_chars_result to_chars_integer_impl(char* first, char
         unsigned_value = static_cast<Unsigned_Integer>(value);
     }
 
+    const std::ptrdiff_t output_length = last - first;
+
     constexpr Unsigned_Integer zero = 48U; // Char for '0'
     constexpr auto buffer_size = sizeof(Unsigned_Integer) * CHAR_BIT;
     char buffer[buffer_size] {};