Redirect user to vis_heap_chunks help when chunks are ommited (#2723)

* redirect user to vis help when chunks are ommited

* fix vis_heap_chunks test by adding help text

pwndbg/commands/ptmalloc2.py

@@ -1004,6 +1004,15 @@ def vis_heap_chunks(
     allocator = pwndbg.aglib.heap.current
     assert isinstance(allocator, GlibcMemoryAllocator)
 
+    # Used to determine whether to show command hint
+    nothing_supplied = (
+        addr is None
+        and count == pwndbg.config.default_visualize_chunk_number
+        and not beyond_top
+        and not no_truncate
+        and not all_chunks
+    )
+
     # If the first argument (count) is big enough (and address isn't provided) interpret it as an address
     if addr is None and count is not None and count > 0x1000:
         addr = count
@@ -1100,6 +1109,7 @@ def vis_heap_chunks(
     cursor = cursor_backup
     chunk = Chunk(cursor)
 
+    reached_top = False
     has_huge_chunk = False
     # round up to align with 4*ptr_size and get half
     half_max_size = (
@@ -1144,6 +1154,7 @@ def vis_heap_chunks(
             labels.extend(bin_labels_map.get(cursor, []))
             if arena is not None and cursor == arena.top:
                 labels.append("Top chunk")
+                reached_top = True
 
             asc += bin_ascii(data)
             if printed % 2 == 0:
@@ -1170,6 +1181,9 @@ def vis_heap_chunks(
             )
         )
 
+    if not reached_top and nothing_supplied:
+        print(message.hint("Not all chunks were shown, see `vis --help` for more information."))
+
 
 VALID_CHARS = list(map(ord, set(printable) - set("\t\r\n\x0c\x0b")))
 

tests/gdb-tests/tests/heap/test_vis_heap_chunks.py

@@ -76,7 +76,9 @@ def test_vis_heap_chunk_command(start_binary):
     gdb.execute("set default-visualize-chunk-number 1")
     assert pwndbg.config.default_visualize_chunk_number == 1
     result = gdb.execute("vis_heap_chunk", to_string=True).splitlines()
-    assert result == expected
+    # No parameters were passed and top isn't reached so help text is shown
+    no_params_help = "Not all chunks were shown, see `vis --help` for more information."
+    assert result == expected + [no_params_help]
     gdb.execute(
         "set default-visualize-chunk-number %d"
         % pwndbg.config.default_visualize_chunk_number.default