sys: implement lol::sys::getenv() for safety.

src/base/features.cpp

@@ -17,8 +17,7 @@ namespace lol
 
 bool has_threads()
 {
-    static char const *var = getenv("LOL_NOTHREADS");
-    static bool const disable_threads = var && var[0];
+    static bool const disable_threads = sys::getenv("LOL_NOTHREADS").size() > 0;
 #if defined __EMSCRIPTEN__ && !defined __EMSCRIPTEN_PTHREADS__
     // For some reason hardware_concurrency() will return the actual number
     // of threads/cores even though the system cannot spawn threads.

src/base/log.cpp

@@ -80,8 +80,7 @@ void msg::helper(message_type type, char const *fmt, va_list ap)
 #if !defined LOL_BUILD_DEBUG && !_DEBUG
     if (type == message_type::debug)
     {
-        static char const *var = getenv("LOL_DEBUG");
-        static bool const disable_debug = !var || !var[0];
+        static bool const disable_debug = sys::getenv("LOL_DEBUG").size() > 0;
         if (disable_debug)
             return;
     }

src/lol/sys/init.h

@@ -19,6 +19,7 @@
 
 #include <string>
 #include <cstdint>
+#include <cstdlib>
 
 namespace lol
 {
@@ -56,6 +57,24 @@ extern void init(int argc, char *argv[],
 extern void add_data_dir(std::string const &dir);
 extern array<std::string> get_path_list(std::string const &file);
 
+static inline std::string getenv(std::string const &var)
+{
+#if _MSC_VER
+    char *buf = nullptr;
+    size_t count = 0;
+    if (_dupenv_s(&buf, &count, var.c_str()) == 0 && buf)
+    {
+        std::string ret(buf);
+        free(buf);
+        return ret;
+    }
+#else
+    if (auto var = std::getenv(var.c_str()))
+        return std::string(var);
+#endif
+    return std::string();
+}
+
 } /* namespace sys */
 
 } /* namespace lol */