list: declare iterator of LIST_FOREACH() in the loop

src/basic/list.h

@@ -136,33 +136,36 @@
 #define LIST_JUST_US(name,item)                                         \
         (!(item)->name##_prev && !(item)->name##_next)
 
+/* The type of the iterator 'i' is automatically determined by the type of 'head', and declared in the
+ * loop. Hence, do not declare the same variable in the outer scope. Sometimes, we set 'head' through
+ * hashmap_get(). In that case, you need to explicitly cast the result. */
 #define LIST_FOREACH(name,i,head)                                       \
-        for ((i) = (head); (i); (i) = (i)->name##_next)
+        for (typeof(*(head)) *i = (head); i; i = i->name##_next)
 
 #define LIST_FOREACH_SAFE(name,i,n,head)                                \
-        for ((i) = (head); (i) && (((n) = (i)->name##_next), 1); (i) = (n))
+        for (typeof(*(head)) *n, *i = (head); i && ((n = i->name##_next), 1); i = n)
 
 #define LIST_FOREACH_BACKWARDS(name,i,p)                                \
-        for ((i) = (p); (i); (i) = (i)->name##_prev)
+        for (typeof(*(p)) *i = (p); i; i = i->name##_prev)
 
 /* Iterate through all the members of the list p is included in, but skip over p */
 #define LIST_FOREACH_OTHERS(name,i,p)                                   \
-        for (({                                                         \
-                (i) = (p);                                              \
-                while ((i) && (i)->name##_prev)                         \
-                        (i) = (i)->name##_prev;                         \
-                if ((i) == (p))                                         \
-                        (i) = (p)->name##_next;                         \
-             });                                                        \
-             (i);                                                       \
-             (i) = (i)->name##_next == (p) ? (p)->name##_next : (i)->name##_next)
+        for (typeof(*(p)) *_p = (p), *i = ({                            \
+                                typeof(*_p) *_j = _p;                   \
+                                while (_j && _j->name##_prev)           \
+                                        _j = _j->name##_prev;           \
+                                if (_j == _p)                           \
+                                        _j = _p->name##_next;           \
+                                _j;                                     \
+                        });                                             \
+             i;                                                         \
+             i = i->name##_next == _p ? _p->name##_next : i->name##_next)
 
-/* Loop starting from p->next until p->prev.
-   p can be adjusted meanwhile. */
+/* Loop starting from p->next until p->prev. p can be adjusted meanwhile. */
 #define LIST_LOOP_BUT_ONE(name,i,head,p)                                \
-        for ((i) = (p)->name##_next ? (p)->name##_next : (head);        \
-             (i) != (p);                                                \
-             (i) = (i)->name##_next ? (i)->name##_next : (head))
+        for (typeof(*(p)) *i = (p)->name##_next ? (p)->name##_next : (head); \
+             i != (p);                                                  \
+             i = i->name##_next ? i->name##_next : (head))
 
 #define LIST_IS_EMPTY(head)                                             \
         (!(head))