ta: add ta_get_parent()

Sometimes useful for debugging. Also fix a random typo elsewhere.

ta/ta.c

@@ -97,7 +97,7 @@ void ta_set_parent(void *ptr, void *ta_parent)
         ch->prev->next = ch->next;
     if (ch->next)
         ch->next->prev = ch->prev;
-    // If ch was the firs child, change child link of old parent
+    // If ch was the first child, change child link of old parent
     if (ch->parent) {
         assert(ch->parent->child == ch);
         ch->parent->child = ch->next;
@@ -119,6 +119,16 @@ void ta_set_parent(void *ptr, void *ta_parent)
     }
 }
 
+/* Return the parent allocation, or NULL if none or if ptr==NULL.
+ *
+ * Warning: do not use this for program logic, or I'll be sad.
+ */
+void *ta_get_parent(void *ptr)
+{
+    struct ta_header *ch = get_header(ptr);
+    return ch ? ch->parent : NULL;
+}
+
 /* Allocate size bytes of memory. If ta_parent is not NULL, this is used as
  * parent allocation (if ta_parent is freed, this allocation is automatically
  * freed as well). size==0 allocates a block of size 0 (i.e. returns non-NULL).

ta/ta.h

@@ -52,6 +52,7 @@ void ta_free(void *ptr);
 void ta_free_children(void *ptr);
 void ta_set_destructor(void *ptr, void (*destructor)(void *));
 void ta_set_parent(void *ptr, void *ta_parent);
+void *ta_get_parent(void *ptr);
 
 // Utility functions
 size_t ta_calc_array_size(size_t element_size, size_t count);