Make "setup_utf8_console" print error message instead of throwing, fi…

…x includes.

src/core/args.hpp

@@ -8,7 +8,6 @@
 
 #include <filesystem>  // for std::filesystem
 #include <stdexcept>   // for std::runtime_error
-#include <string>      // for std::string
 #include <vector>      // for std::vector
 
 namespace core::args {

src/core/io.cpp

@@ -12,6 +12,7 @@
 #if defined(_WIN32)
 #define WIN32_LEAN_AND_MEAN  // Exclude rarely-used stuff from Windows headers
 #include <locale>            // for setlocale, LC_ALL
+#include <optional>          // for std::optional, std::nullopt
 #include <windows.h>         // for CP_UTF8, SetConsoleCP, SetConsoleOutputCP, GetLastError
 #endif
 
@@ -21,19 +22,24 @@
 
 namespace core::io {
 
-void setup_utf8_console()
+#if defined(_WIN32)
+
+std::optional<std::string> setup_utf8_console()
 {
 #if defined(_WIN32)
     if (!SetConsoleCP(CP_UTF8) || !SetConsoleOutputCP(CP_UTF8)) {
-        throw std::runtime_error(fmt::format("Failed to set UTF-8 code page: {}", GetLastError()));
+        return fmt::format("Failed to set UTF-8 code page: {}", GetLastError());
     }
 
     if (!setlocale(LC_ALL, ".UTF8")) {
-        throw std::runtime_error("Failed to set UTF-8 locale");
+        return "Failed to set UTF-8 locale";
     }
 #endif
+    return std::nullopt;
 }
 
+#endif
+
 std::vector<Line> read_lines(const std::filesystem::path &input_path,
                              const std::size_t initial_capacity)
 {

src/core/io.hpp

@@ -10,15 +10,22 @@
 #include <filesystem>  // for std::filesystem
 #include <string>      // for std::string
 #include <vector>      // for std::vector
+#if defined(_WIN32)
+#include <optional>  // for std::optional
+#endif
 
 namespace core::io {
 
+#if defined(_WIN32)
+
 /**
  * @brief Setup UTF-8 input/output on Windows. Do nothing on other platforms.
  *
- * @throws std::runtime_error If failed to enable UTF-8 encoding on Windows.
+ * @return Error message if the setup fails, "std::nullopt" otherwise.
  */
-void setup_utf8_console();
+[[nodiscard]] std::optional<std::string> setup_utf8_console();
+
+#endif
 
 /**
  * @brief Struct that represents a single line of text.

src/main.cpp

@@ -27,7 +27,9 @@ int main(int argc,
     try {
 #if defined(_WIN32)
         // Setup UTF-8 input/output on Windows (does nothing on other platforms)
-        core::io::setup_utf8_console();
+        if (const auto e = core::io::setup_utf8_console(); e.has_value()) {
+            fmt::print(stderr, "Warning: {}\n", *e);
+        }
 #endif
 
         // Pass parsed command-line arguments to the application