visualize-links 1.0.1

An LLDB plugin and web ui to visualize and debug pointer-based data structure programs written in C/C++.

visualize-links

An LLDB debugger plugin and web ui to visualize and debug pointer-based data structure programs written in C/C++."

visualize-links provides a python LLDB plugin with custom commands to visualize program variables and expressions. It also contains an interactive web ui acting as the canvas where generated graphs are shown.

Pointer-based data structures are represented as graphs where each node represents a value and each edge represents directed links between values through member attributes.

Installation

Install LLDB. Note that test scripts are hardcoded to use lldb-19 whenever required.

Install visualize-links package and auto-import it on LLDB session start.

$ pip install visualize-links && echo "command script import visualize_links" >> ~/.lldbinit

Usage

Usage is shown using a sample program that implements the following linked list problem: Reverse Nodes in k-Group.

• Given the head of a linked list, reverse the nodes of the list k at a time, and return the modified list.
• The example can be found at tests/list_reverse_k_group.cpp and ran as follows.

make launch_test TARGET=list_reverse_k_group

This performs the following tasks:

• Builds the target program: $(TARGET).cpp
• Launches ui in browser: $ visualize-links-ui
• Starts an lldb session: lldb $(TARGET)
• Executes a sample set of lldb commands: $(TARGET).lldb

The plugin exposes the following lldb commands for visualization.

• visualize-expr EXPR
  • Create a graph starting from EXPR. Values unreachable from EXPR are not traced.
• visualize-type TYPE
  • Create a graph starting from all active variables pointing to a value of type TYPE.
• visualize-history
  • Show a list of past graphs generated with the above two commands along with their unique ids. History is also shown on the right pane of the ui.
• visualize-diff UID1 UID2
  • Create an asymmetric difference graph showing how the graphs corresponding to UID1 and UID2 differ. Difference graph can be created from the ui directly as well.

For demonstration, list_reverse_k_group.lldb is shown below with comments:

(lldb) # add a breakpoint after the initial list l is created [0,1,2,3,4]
(lldb) b list_reverse_k_group.cpp:63
(lldb) # add a breakpoint after l2 points to the intended new list [2,1,0,3,4]
(lldb) b list_reverse_k_group.cpp:66
(lldb) run
(lldb) # visualize the list pointed by l
(lldb) visualize-expr l
(lldb) continue
(lldb) # visualize the new list pointed by l2
(lldb) visualize-expr l2
(lldb) # visualize lists from l & l2
(lldb) visualize-type ListNode
(lldb) # visualize the transformation performed by reverseKGroup()
(lldb) visualize-diff 0 1

License

This project is licensed under the MIT License - see the LICENSE file for details.