refactor: get_environment_variable() function in libutil (#505)

Author: benthevining

ben-bot/CMakeLists.txt

@@ -18,10 +18,6 @@ target_link_libraries (ben_bot PRIVATE ben_bot::libbenbot)
 
 add_executable (ben_bot::ben_bot ALIAS ben_bot)
 
-if (MSVC)
-    target_compile_definitions (ben_bot PRIVATE _CRT_SECURE_NO_WARNINGS)
-endif ()
-
 #
 
 include (CheckIPOSupported)

ben-bot/main.cpp

@@ -23,6 +23,7 @@
 #include <libbenbot/engine/Engine.hpp>
 #include <libchess/uci/Printing.hpp>
 #include <libutil/Console.hpp>
+#include <libutil/Environment.hpp>
 #include <span>
 #include <string>
 #include <string_view>
@@ -110,8 +111,13 @@ try {
 
     ben_bot::Engine engine;
 
-    if (const auto* var = std::getenv("BENBOT_CONFIG"))
-        engine.read_config_file(std::filesystem::path { var });
+    util::get_environment_variable("BENBOT_CONFIG")
+        .transform([&engine](const string_view value) {
+            if (not value.empty())
+                engine.read_config_file(std::filesystem::path { value });
+
+            return std::monostate { };
+        });
 
     if (not uciCommand.empty())
         engine.handle_command(uciCommand);

libutil/include/libutil/Environment.hpp

@@ -0,0 +1,41 @@
+/*
+ * ======================================================================================
+ *
+ * ░▒▓███████▓▒░░▒▓████████▓▒░▒▓███████▓▒░       ░▒▓███████▓▒░ ░▒▓██████▓▒░▒▓████████▓▒░
+ * ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░ ░▒▓█▓▒░
+ * ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░ ░▒▓█▓▒░
+ * ░▒▓███████▓▒░░▒▓██████▓▒░ ░▒▓█▓▒░░▒▓█▓▒░      ░▒▓███████▓▒░░▒▓█▓▒░░▒▓█▓▒░ ░▒▓█▓▒░
+ * ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░ ░▒▓█▓▒░
+ * ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░ ░▒▓█▓▒░
+ * ░▒▓███████▓▒░░▒▓████████▓▒░▒▓█▓▒░░▒▓█▓▒░      ░▒▓███████▓▒░ ░▒▓██████▓▒░  ░▒▓█▓▒░
+ *
+ * ======================================================================================
+ */
+
+/** @file
+    This file provides functions for working with environment variables.
+    @ingroup util
+ */
+
+#pragma once
+
+#include <optional>
+#include <string>
+#include <string_view>
+
+namespace util {
+
+/** Returns the value of the environment variable with the given name.
+    If the variable is not set, or there is an error querying the
+    environment, ``nullopt`` is returned. If the variable is set to an
+    empty string, an optional holding an empty string is returned.
+
+    @note This function is needed because all compilers warn about
+    ``std::getenv()`` being deprecated and/or thread-unsafe. This
+    function abstracts platform-specific thread-safe versions of
+    ``std::getenv()``.
+ */
+[[nodiscard]] auto get_environment_variable(std::string_view name)
+    -> std::optional<std::string>;
+
+} // namespace util

libutil/src/Environment.cpp

@@ -0,0 +1,60 @@
+/*
+ * ======================================================================================
+ *
+ * ░▒▓███████▓▒░░▒▓████████▓▒░▒▓███████▓▒░       ░▒▓███████▓▒░ ░▒▓██████▓▒░▒▓████████▓▒░
+ * ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░ ░▒▓█▓▒░
+ * ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░ ░▒▓█▓▒░
+ * ░▒▓███████▓▒░░▒▓██████▓▒░ ░▒▓█▓▒░░▒▓█▓▒░      ░▒▓███████▓▒░░▒▓█▓▒░░▒▓█▓▒░ ░▒▓█▓▒░
+ * ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░ ░▒▓█▓▒░
+ * ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░      ░▒▓█▓▒░░▒▓█▓▒░▒▓█▓▒░░▒▓█▓▒░ ░▒▓█▓▒░
+ * ░▒▓███████▓▒░░▒▓████████▓▒░▒▓█▓▒░░▒▓█▓▒░      ░▒▓███████▓▒░ ░▒▓██████▓▒░  ░▒▓█▓▒░
+ *
+ * ======================================================================================
+ */
+
+#include <cstdlib> // IWYU pragma: keep - for std::getenv()
+#include <libutil/Environment.hpp>
+#include <optional>
+#include <string>
+#include <string_view>
+
+namespace util {
+
+using std::optional;
+using std::string;
+using std::string_view;
+
+namespace {
+#ifdef _MSC_VER
+    [[nodiscard]] auto get_env_var_internal(const char* name) -> optional<string>
+    {
+        char*  value { nullptr };
+        size_t len { 0uz };
+
+        [[maybe_unused]] const auto err = _dupenv_s(&value, &len, name);
+
+        if (value != nullptr and len > 0uz)
+            return string { value, len };
+
+        return std::nullopt;
+    }
+#else
+    [[nodiscard]] auto get_env_var_internal(const char* name) -> optional<string>
+    {
+        if (const auto* value = std::getenv(name))
+            return { value };
+
+        return std::nullopt;
+    }
+#endif
+} // namespace
+
+auto get_environment_variable(const string_view name) -> optional<string>
+{
+    // This is needed because string_view::data() may not be null-terminated
+    const string nameStr { name };
+
+    return get_env_var_internal(nameStr.c_str());
+}
+
+} // namespace util