Fix mutation of input iterators in seq_arr_erase_it

The seq_arr_erase_it function was modifying start_it during the free_func loop,
which led to incorrectly apply the free_func on the whole array.

This commit makes sure the elements "freed" are only those in the range and not the whole seq_arr.

* Fixes the logic by introducing a temporary iterator for the free loop,
  preserving start_it and end_it for correct offset calculations.

* Adds a regression test in test_seq_arr to verify that only the selected
  subrange is erased and that free_func is called exactly on that range.

common/utils/ds/seq_arr.c

@@ -123,11 +123,10 @@ void seq_arr_erase_it(seq_arr_t* arr, void* start_it, void* end_it, void (*free_
     return;
 
   if (free_func != NULL) {
-    void* start_it = seq_arr_front(arr);
-    void* end_it = seq_arr_end(arr);
-    while (start_it != end_it) {
-      free_func(start_it);
-      start_it = seq_arr_next(arr, start_it);
+    void* it = start_it;
+    while (it != end_it) {
+      free_func(it);
+      it = seq_arr_next(arr, it);
     }
   }
 

common/utils/ds/tests/test_seq_array.c

@@ -36,6 +36,13 @@ static int compar(const void* m0, const void* m1)
   return 1;
 }
 
+static int free_func_call_count = 0;
+
+static void dummy_free_func(void* it)
+{
+  ++free_func_call_count;
+}
+
 int main()
 {
   seq_arr_t arr = {0};
@@ -83,6 +90,19 @@ int main()
   void* it = bsearch(&key, base, nmemb, size, compar);
   assert(seq_arr_dist(&arr, seq_arr_front(&arr), it) == 4);
 
+  // Regression test: erase a partial range only
+  // Erase 92, 93, 94 (i.e., indices 1 to 3)
+  int* start = seq_arr_at(&arr, 1);
+  int* end = seq_arr_at(&arr, 4);
+  seq_arr_erase_it(&arr, start, end, dummy_free_func);
+
+  // Now values should be: [91, 95, 96, 97, 98, 99]
+  assert(free_func_call_count == 3);
+  assert(seq_arr_size(&arr) == 6);
+  assert(*(int*)seq_arr_at(&arr, 0) == 91);
+  assert(*(int*)seq_arr_at(&arr, 1) == 95);
+  assert(*(int*)seq_arr_at(&arr, 5) == 99);
+
   // Free data structure
   seq_arr_free(&arr, NULL);