Add compile-time helper methods for testing compiler support

And add missing fly.cpp unit test to Windows build.

Author: trflynn89

build/win/libfly_unit_tests/libfly_unit_tests.vcxproj

@@ -210,6 +210,7 @@
     </ProjectReference>
   </ItemGroup>
   <ItemGroup>
+    <ClCompile Include="..\..\..\test\fly.cpp" />
     <ClCompile Include="..\..\..\test\main.cpp" />
     <ClCompile Include="..\..\..\test\coders\base64_coder.cpp" />
     <ClCompile Include="..\..\..\test\coders\huffman_coder.cpp" />

build/win/libfly_unit_tests/libfly_unit_tests.vcxproj.filters

@@ -33,6 +33,7 @@
     </Filter>
   </ItemGroup>
   <ItemGroup>
+    <ClCompile Include="..\..\..\test\fly.cpp" />
     <ClCompile Include="..\..\..\test\main.cpp" />
     <ClCompile Include="..\..\..\test\coders\base64_coder.cpp">
       <Filter>coders</Filter>

fly/fly.hpp

@@ -11,6 +11,29 @@
 #    error Unsupported operating system. Only Linux, macOS, and Windows are supported.
 #endif
 
+// Detect compiler.
+#if defined(__clang__)
+#    define FLY_COMPILER_CLANG
+#elif defined(__GNUC__)
+#    define FLY_COMPILER_GCC
+#elif defined(_MSC_VER)
+#    define FLY_COMPILER_MSVC
+#else
+#    warning Unsupported compiler. Only Clang, GCC, and MSVC are supported.
+#endif
+
+// Detect language feature support. See: https://en.cppreference.com/w/cpp/compiler_support
+#if defined(FLY_COMPILER_DISABLE_CONSTEVAL)
+#    undef FLY_COMPILER_SUPPORTS_CONSTEVAL
+#    define FLY_CONSTEVAL constexpr
+#elif defined(FLY_COMPILER_GCC)
+#    define FLY_COMPILER_SUPPORTS_CONSTEVAL
+#    define FLY_CONSTEVAL consteval
+#else
+#    undef FLY_COMPILER_SUPPORTS_CONSTEVAL
+#    define FLY_CONSTEVAL constexpr
+#endif
+
 // Define macro to convert a macro parameter to a string.
 #define FLY_STRINGIZE(s) #s
 
@@ -77,4 +100,60 @@ inline constexpr bool is_windows()
 #endif
 }
 
+/**
+ * Compile-time helper function to determine if the compiler is Clang.
+ *
+ * @return True if the compiler is Clang.
+ */
+inline constexpr bool is_clang()
+{
+#if defined(FLY_COMPILER_CLANG)
+    return true;
+#else
+    return false;
+#endif
+}
+
+/**
+ * Compile-time helper function to determine if the compiler is GCC.
+ *
+ * @return True if the compiler is GCC.
+ */
+inline constexpr bool is_gcc()
+{
+#if defined(FLY_COMPILER_GCC)
+    return true;
+#else
+    return false;
+#endif
+}
+
+/**
+ * Compile-time helper function to determine if the compiler is MSVC.
+ *
+ * @return True if the compiler is Clang.
+ */
+inline constexpr bool is_msvc()
+{
+#if defined(FLY_COMPILER_MSVC)
+    return true;
+#else
+    return false;
+#endif
+}
+
+/**
+ * Compile-time helper function to determine if immediate functions (consteval) are supported.
+ *
+ * @return True if the compiler supports consteval.
+ */
+inline constexpr bool supports_consteval()
+{
+#if defined(FLY_COMPILER_SUPPORTS_CONSTEVAL)
+    return true;
+#else
+    return false;
+#endif
+}
+
 } // namespace fly

test/fly.cpp

@@ -8,11 +8,8 @@ CATCH_TEST_CASE("Fly", "[fly]")
 {
     CATCH_SECTION("Stringize helper")
     {
-        const std::string s1 = FLY_STRINGIZE();
-        CATCH_CHECK(s1.empty());
-
-        const std::string s2 = FLY_STRINGIZE(libfly);
-        CATCH_CHECK(s2 == "libfly");
+        const std::string s = FLY_STRINGIZE(libfly);
+        CATCH_CHECK(s == "libfly");
     }
 
     CATCH_SECTION("Operating system-dependent headers")
@@ -50,6 +47,38 @@ CATCH_TEST_CASE("Fly", "[fly]")
         CATCH_CHECK(fly::is_windows());
 #else
         static_assert(false, "Unknown operating system");
+#endif
+    }
+
+    CATCH_SECTION("Compiler helpers")
+    {
+#if defined(__clang__)
+        CATCH_CHECK(fly::is_clang());
+        CATCH_CHECK_FALSE(fly::is_gcc());
+        CATCH_CHECK_FALSE(fly::is_msvc());
+#elif defined(__GNUC__)
+        CATCH_CHECK_FALSE(fly::is_clang());
+        CATCH_CHECK(fly::is_gcc());
+        CATCH_CHECK_FALSE(fly::is_msvc());
+#elif defined(_MSC_VER)
+        CATCH_CHECK_FALSE(fly::is_clang());
+        CATCH_CHECK_FALSE(fly::is_gcc());
+        CATCH_CHECK(fly::is_msvc());
+#else
+        static_assert(false, "Unknown compiler");
+#endif
+    }
+
+    CATCH_SECTION("Language feature helpers")
+    {
+#if defined(__clang__)
+        CATCH_CHECK_FALSE(fly::supports_consteval());
+#elif defined(__GNUC__)
+        CATCH_CHECK(fly::supports_consteval());
+#elif defined(_MSC_VER)
+        CATCH_CHECK_FALSE(fly::supports_consteval());
+#else
+        static_assert(false, "Unknown compiler");
 #endif
     }
 }