Use std::getenv #3414 (#3415)

Author: kfeng123

include/spdlog/cfg/helpers-inl.h

@@ -71,7 +71,7 @@ inline std::unordered_map<std::string, std::string> extract_key_vals_(const std:
 }
 
 SPDLOG_INLINE void load_levels(const std::string &input) {
-    if (input.empty() || input.size() > 512) {
+    if (input.empty() || input.size() >= 32768) {
         return;
     }
 

include/spdlog/details/os-inl.h

@@ -563,21 +563,21 @@ SPDLOG_INLINE filename_t dir_name(const filename_t &path) {
     return pos != filename_t::npos ? path.substr(0, pos) : filename_t{};
 }
 
+#ifdef _MSC_VER
+    #pragma warning(push)
+    #pragma warning(disable : 4996)
+#endif  // _MSC_VER
 std::string SPDLOG_INLINE getenv(const char *field) {
-#if defined(_MSC_VER)
-    #if defined(__cplusplus_winrt)
+#if defined(_MSC_VER) && defined(__cplusplus_winrt)
     return std::string{};  // not supported under uwp
-    #else
-    size_t len = 0;
-    char buf[128];
-    bool ok = ::getenv_s(&len, buf, sizeof(buf), field) == 0;
-    return ok ? buf : std::string{};
-    #endif
-#else  // revert to getenv
-    char *buf = ::getenv(field);
+#else
+    char *buf = std::getenv(field);
     return buf ? buf : std::string{};
 #endif
 }
+#ifdef _MSC_VER
+    #pragma warning(pop)
+#endif  // _MSC_VER
 
 // Do fsync by FILE handlerpointer
 // Return true on success