move next_index inside emutls_control struct

Author: semarie

lib/std/special/compiler_rt/emutls.zig

@@ -24,9 +24,6 @@ comptime {
     assert(std.builtin.link_libc);
 }
 
-// global counter for keeping track of requested indexes.
-var global_index: usize = 1;
-
 /// public entrypoint for generated code using EmulatedTLS
 pub fn __emutls_get_address(control: *emutls_control) callconv(.C) *c_void {
     return control.getPointer();
@@ -245,6 +242,10 @@ const emutls_control = extern struct {
     // global Mutex used to serialize control.index initialization.
     var mutex: std.c.pthread_mutex_t = std.c.PTHREAD_MUTEX_INITIALIZER;
 
+    // global counter for keeping track of requested indexes.
+    // access should be done with mutex held.
+    var next_index: usize = 1;
+
     /// Simple wrapper for global lock.
     fn lock() void {
         if (std.c.pthread_mutex_lock(&emutls_control.mutex) != 0) {
@@ -282,10 +283,10 @@ const emutls_control = extern struct {
         }
 
         // Store a new index atomically (for having coherent index_lockless reading).
-        @atomicStore(usize, &self.object.index, global_index, .Release);
+        @atomicStore(usize, &self.object.index, emutls_control.next_index, .Release);
 
         // Increment the next available index
-        global_index += 1;
+        emutls_control.next_index += 1;
 
         return self.object.index;
     }