diff --git a/build_tool/library.cpp b/build_tool/library.cpp
index 28f35d1..061a41c 100644
--- a/build_tool/library.cpp
+++ b/build_tool/library.cpp
@@ -12,9 +12,8 @@
 #define AND_CL_STRING_TERMINATE_ON_NEW_LINE
 #include "../standalone_libraries/clexer.c"
 
-MA_Arena PernamentArena;
-MA_Arena *Perm = &PernamentArena;
-Table<S8_String> CMDLine;
+thread_local MA_Arena PernamentArena;
+thread_local MA_Arena *Perm = &PernamentArena;
 
 #include "cache.cpp"
 #include "easy_strings.cpp"
diff --git a/standalone_libraries/io.c b/standalone_libraries/io.c
index f600287..b15f9b6 100644
--- a/standalone_libraries/io.c
+++ b/standalone_libraries/io.c
@@ -31,7 +31,7 @@ IO_StaticFunc int IO_Strlen(char *string) {
     return len;
 }
 
-void (*IO_User_OutputMessage)(int kind, const char *file, int line, char *str, int len);
+IO_THREAD_LOCAL void (*IO_User_OutputMessage)(int kind, const char *file, int line, char *str, int len);
 
 IO_API bool IO__FatalErrorf(const char *file, int line, const char *msg, ...) {
     va_list args1;
diff --git a/standalone_libraries/io.h b/standalone_libraries/io.h
index 72b8711..6c325d5 100644
--- a/standalone_libraries/io.h
+++ b/standalone_libraries/io.h
@@ -22,6 +22,22 @@ typedef enum IO_ErrorResult {
     #define IO_DebugBreak() (__builtin_trap(), 0)
 #endif
 
+#ifndef IO_THREAD_LOCAL
+    #if defined(__cplusplus) && __cplusplus >= 201103L
+        #define IO_THREAD_LOCAL thread_local
+    #elif defined(__GNUC__)
+        #define IO_THREAD_LOCAL __thread
+    #elif defined(_MSC_VER)
+        #define IO_THREAD_LOCAL __declspec(thread)
+    #elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L && !defined(__STDC_NO_THREADS__)
+        #define IO_THREAD_LOCAL _Thread_local
+    #elif defined(__TINYC__)
+        #define IO_THREAD_LOCAL _Thread_local
+    #else
+        #error Couldnt figure out thread local, needs to be provided manually
+    #endif
+#endif
+
 #if defined(__has_attribute)
     #if __has_attribute(format)
         #define IO__PrintfFormat(fmt, va) __attribute__((format(printf, fmt, va)))
@@ -33,7 +49,7 @@ typedef enum IO_ErrorResult {
 #endif
 
 typedef void IO_MessageHandler(int kind, const char *file, int line, char *str, int len);
-extern void (*IO_User_OutputMessage)(int kind, const char *file, int line, char *str, int len);
+extern IO_THREAD_LOCAL void (*IO_User_OutputMessage)(int kind, const char *file, int line, char *str, int len);
 
 #define IO__STRINGIFY(x) #x
 #define IO__TOSTRING(x) IO__STRINGIFY(x)