Watch your C++ grow, one call at a time.
See how your C++ program runs: follow recursive calls, inspect variables, watch pointers connect, and step backward when something surprises you. StackBloom records a real execution under GDB and lets you explore it in your browser.
Built for learning recursion, dynamic programming, and data structures with single-file C++17 programs. Runs locally; no account needed.
Get started · User guide · Development
Choose one option:
| Your setup | Start here |
|---|---|
| Windows, without a development toolchain | Download the portable app below |
| Docker installed | Build and run the container below |
| Working from source | Follow the Windows or Ubuntu setup |
- Download
StackBloom-windows-x64.zipfrom Releases. If there is no release asset, check the Windows build artifacts. - Extract it to a short path, such as
C:\StackBloom. - Open the extracted folder and double-click StackBloom.cmd.
The compiler, debugger, Python, and viewer are included. Your browser opens the editor. Windows setup details
From a checkout of this repository:
docker build -t stackbloom .
docker run --rm -p 127.0.0.1:8765:8765 stackbloomOpen localhost:8765. Docker options
Run only code you trust. StackBloom is not a sandbox. Keep the server local; do not expose it through a public port or tunnel.
- Choose Fibonacci in the editor and leave its example input in place.
- Click Run & visualize, then open Recursion tree.
- Press Step to follow one stop, or Play to watch the calls unfold.
- Step backward or drag the timeline to revisit a moment.
The highlighted source line is the next line to execute. Replay reads the recording; it does not run your program again.
Once that feels familiar, try Grid paths and open Tables to watch a DP table fill, Memo Fibonacci to inspect a memo map, or Linked list and open Memory to follow pointers.
Practising on LeetCode? Switch the editor to LeetCode solution, paste your
class Solution (or plain functions with your own Node struct), and copy the example
test case (nums = [2,7,11,15], target = 9). StackBloom writes main(), builds lists
and trees, and prints the result.
LeetCode mode details
| When you want to… | Use… |
|---|---|
Trace a LeetCode answer, or any function, without writing main() |
LeetCode solution in the editor |
| Inspect each call's variables | Call stack, with Watch to pin a value |
| Understand recursion and returns | Recursion tree, with Predict to test a guess |
| Watch a BFS or DFS walk an adjacency list | Graph, which appears when the program builds one |
| Find repeated calls | Repeated work, which highlights matching call labels |
| Read map/set contents | Call stack or Memory, with new and changed entries marked |
| See arrays and DP updates | Tables, with changed cells and loop-index markers; Bars for sorting and searching |
| Follow pointers, aliases, and heap objects | Memory |
| Revisit or share a run | The timeline, Download for JSON, or Export for images, animations, or one HTML file anyone can open |
You do not need every control to get started. The user guide covers stepping, graph navigation, predictions, and exports.
- One C++17 source file per run; multi-file projects and custom build flags are not supported.
- Thread creation stops tracing as unsupported.
- STL display depends on the compiler's pretty-printers. Unknown types, pointer targets, and initialization states cannot always be resolved.
- Traces have step, time, output, and inspection limits. They show recorded observations, not proof that a program is free of undefined behavior.
- Repeated call labels are a heuristic, not proof that results can be memoized.
Read the execution boundaries before relying on a trace for anything beyond exploration.
- Installation and startup
- User guide and screenshot tour
- Development, CLI, and tests
- Architecture and data flow · Trace schema · Roadmap
- Product principles · Visual design system
GPL-3.0-or-later. Your submitted programs and recorded traces remain
yours. The allocation recorder includes an additional
permission for the code it links into your program. Portable distributions list
bundled dependencies and their sources in THIRD_PARTY.md.