diff --git a/src/utility/rng.hpp b/src/utility/rng.hpp
index f1d094b0..8f2d123c 100644
--- a/src/utility/rng.hpp
+++ b/src/utility/rng.hpp
@@ -475,12 +475,12 @@ namespace gapp::rng
     template<std::integral IntType>
     small_vector<IntType> sampleUnique(IntType lbound, IntType ubound, size_t count)
     {
-        const size_t GAPP_MAY_ALIAS range_len = detail::range_length(lbound, ubound);
+        const std::uint64_t GAPP_MAY_ALIAS range_len = detail::range_length(lbound, ubound);
 
         GAPP_ASSERT(ubound >= lbound);
         GAPP_ASSERT(range_len >= count);
 
-        const bool GAPP_MAY_ALIAS select_many = std::cmp_greater_equal(count, size_t(0.6 * range_len));
+        const bool GAPP_MAY_ALIAS select_many = std::cmp_greater_equal(count, std::uint64_t(0.6 * range_len));
         const bool GAPP_MAY_ALIAS huge_range = std::cmp_greater_equal(range_len, 65536);
 
         if (huge_range) return rng::sampleUniqueSet(lbound, ubound, count);
diff --git a/src/utility/small_vector.hpp b/src/utility/small_vector.hpp
index 11c1cf74..aecb4dda 100644
--- a/src/utility/small_vector.hpp
+++ b/src/utility/small_vector.hpp
@@ -167,7 +167,7 @@ namespace gapp::detail
         {
             if (!std::is_constant_evaluated())
             {
-                std::fill((char*)first, (char*)last, 0);
+                std::fill((unsigned char*)first, (unsigned char*)last, 0);
                 return;
             }
         }
@@ -200,8 +200,8 @@ namespace gapp::detail
         {
             if (!std::is_constant_evaluated())
             {
-                char* src = (char*)std::to_address(src_first);
-                std::copy(src, src + sizeof(T) * (last - first), (char*)first);
+                unsigned char* src = (unsigned char*)std::to_address(src_first);
+                std::copy(src, src + sizeof(T) * (last - first), (unsigned char*)first);
                 return;
             }
         }
@@ -221,7 +221,7 @@ namespace gapp::detail
         {
             if (!std::is_constant_evaluated())
             {
-                std::copy((char*)first, (char*)last, (char*)dest);
+                std::copy((unsigned char*)first, (unsigned char*)last, (unsigned char*)dest);
                 return;
             }
         }
@@ -241,7 +241,7 @@ namespace gapp::detail
         {
             if (!std::is_constant_evaluated())
             {
-                std::copy((char*)first, (char*)last, (char*)dest);
+                std::copy((unsigned char*)first, (unsigned char*)last, (unsigned char*)dest);
                 return;
             }
         }
diff --git a/src/utility/utility.hpp b/src/utility/utility.hpp
index b7c2f223..2a2325a3 100644
--- a/src/utility/utility.hpp
+++ b/src/utility/utility.hpp
@@ -1,12 +1,13 @@
 /* Copyright (c) 2022 Krisztián Rugási. Subject to the MIT License. */
 
-#ifndef GA_UTILITY_UTILITY_HPP
-#define GA_UTILITY_UTILITY_HPP
+#ifndef GAPP_UTILITY_UTILITY_HPP
+#define GAPP_UTILITY_UTILITY_HPP
 
 #include <vector>
 #include <concepts>
 #include <type_traits>
 #include <cassert>
+#include <cstdint>
 #include <cstddef>
 
 
@@ -75,13 +76,6 @@
 #endif
 
 
-#if defined(__GNUC__) || defined(__clang__)
-#   define GAPP_NON_NULL __attribute__((nonnull))
-#else
-#   define GAPP_NON_NULL
-#endif
-
-
 #if defined(__GNUC__) || defined(__clang__)
 #   define GAPP_MAY_ALIAS __attribute__((may_alias))
 #else
@@ -185,27 +179,13 @@ namespace gapp::detail
         temp.swap(vec);
     }
 
-    // returns true if the signs of the parameters are the same
-    template<std::signed_integral T>
-    constexpr bool same_sign(T left, T right) noexcept
-    {
-        return (left ^ right) >= 0;
-    }
-
-    // returns the length of the range [low, high) without overflow
+    // returns the length of the range [low, high] without overflow
     template<std::integral T>
-    constexpr size_t range_length(T low, T high) noexcept
+    constexpr std::uint64_t range_length(T low, T high) noexcept
     {
         GAPP_ASSERT(low <= high);
 
-        if constexpr (std::is_unsigned_v<T>)
-        {
-            return high - low;
-        }
-        else
-        {
-            return same_sign(low, high) ? high - low : size_t(-(low + 1)) + high + 1;
-        }
+        return std::uint64_t(high) - std::uint64_t(low);
     }
 
     template<std::integral T>
@@ -240,4 +220,4 @@ namespace gapp::detail
 
 } // namespace gapp::detail
 
-#endif // !GA_UTILITY_UTILITY_HPP
\ No newline at end of file
+#endif // !GAPP_UTILITY_UTILITY_HPP
diff --git a/test/unit/utility.cpp b/test/unit/utility.cpp
new file mode 100644
index 00000000..81fc0b20
--- /dev/null
+++ b/test/unit/utility.cpp
@@ -0,0 +1,55 @@
+/* Copyright (c) 2024 Krisztián Rugási. Subject to the MIT License. */
+
+#include <catch2/catch_test_macros.hpp>
+#include <catch2/catch_template_test_macros.hpp>
+#include "utility/utility.hpp"
+#include <type_traits>
+#include <limits>
+#include <cstdint>
+
+using namespace gapp;
+using namespace gapp::detail;
+
+
+TEMPLATE_TEST_CASE("range_length_signed", "[utility]", std::int8_t, std::int16_t, std::int32_t, std::int64_t)
+{
+    using IntType  = TestType;
+    using UIntType = std::make_unsigned_t<IntType>;
+
+    constexpr IntType small = std::numeric_limits<IntType>::min();
+    constexpr IntType large = std::numeric_limits<IntType>::max();
+
+    STATIC_REQUIRE(range_length(IntType{ 0 }, IntType{ 0 }) == 0);
+    STATIC_REQUIRE(range_length(IntType{ -1 }, IntType{ -1 }) == 0);
+    STATIC_REQUIRE(range_length(IntType{ 1 }, IntType{ 1 }) == 0);
+
+    STATIC_REQUIRE(range_length(IntType{ 0 }, IntType{ 1 }) == 1);
+    STATIC_REQUIRE(range_length(IntType{ -1 }, IntType{ 0 }) == 1);
+
+    STATIC_REQUIRE(range_length(IntType{ -1 }, IntType{ 1 }) == 2);
+
+    STATIC_REQUIRE(range_length(small, small) == 0);
+    STATIC_REQUIRE(range_length(large, large) == 0);
+
+    STATIC_REQUIRE(range_length(small, IntType{ 0 }) == (UIntType(large) + 1));
+    STATIC_REQUIRE(range_length(IntType{ 0 }, large) == UIntType(large));
+    STATIC_REQUIRE(range_length(small, large) == std::numeric_limits<UIntType>::max());
+}
+
+TEMPLATE_TEST_CASE("range_length_unsigned", "[utility]", std::uint8_t, std::uint16_t, std::uint32_t, std::uint64_t)
+{
+    using IntType = TestType;
+
+    constexpr IntType small = std::numeric_limits<IntType>::min();
+    constexpr IntType large = std::numeric_limits<IntType>::max();
+
+    STATIC_REQUIRE(range_length(IntType{ 0 }, IntType{ 0 }) == 0);
+    STATIC_REQUIRE(range_length(IntType{ 1 }, IntType{ 1 }) == 0);
+
+    STATIC_REQUIRE(range_length(IntType{ 0 }, IntType{ 1 }) == 1);
+
+    STATIC_REQUIRE(range_length(small, small) == 0);
+    STATIC_REQUIRE(range_length(large, large) == 0);
+
+    STATIC_REQUIRE(range_length(small, large) == large);
+}