ThreadX: Support for __DYNAMIC_REENT__

- ThreadX change to handle dynamic reent for both newlib and xclib
- Adapt ThreadX xclib interface code to handle dynamic reent pointers

Author: ianstcdns

ports/xtensa/xcc/src/tx_clib_lock.c

@@ -136,6 +136,12 @@ __env_unlock (struct _reent * ptr)
 #include <errno.h>
 #include <sys/reent.h>
 
+#if defined(__DYNAMIC_REENT__)
+// Helps to keep code similar between dynamic and non-dynamic.
+#undef _reent_ptr
+struct _reent * _reent_ptr;
+#endif
+
 #define XT_NUM_CLIB_LOCKS      (_MAX_LOCK + FOPEN_MAX)
 
 typedef TX_MUTEX * _Rmtx;
@@ -209,6 +215,31 @@ _Mtxunlock (_Rmtx * mtx)
 
 #endif /* XSHAL_CLIB == XTHAL_CLIB_XCLIB */
 
+#if defined(__DYNAMIC_REENT__)
+/**************************************************************************/
+/*    Return libc context pointer for current thread. Overrides weak      */
+/*    version in libc. Until real threads are active, use the libc's      */
+/*    global reent struct.                                                */
+/**************************************************************************/
+struct _reent *
+__getreent(void)
+{
+    TX_THREAD * thread_ptr = _tx_thread_current_ptr;
+
+    if (thread_ptr) {
+        return &(thread_ptr->tx_thread_clib_reent);
+    }
+
+#if XSHAL_CLIB == XTHAL_CLIB_XCLIB
+    extern struct _reent g_reent; /* from xclib */
+    return &g_reent;
+#endif
+#if XSHAL_CLIB == XTHAL_CLIB_NEWLIB
+    extern struct _reent * _impure_ptr; /* from newlib */
+    return _impure_ptr;
+#endif
+}
+#endif
 
 /**************************************************************************/
 /*    _sbrk_r - heap allocator. This function is called when the memory   */