Files
visual_debugger/scripts/dump_debug_graph.py
mynameisdeleted a8d105005e feat(debug): add GDB-based debug visualizer for linked lists
Replace the custom toDebugGraph() method that generated JSON directly in C++ with a generic GDB Python script (debug_graph.py). The script traverses pointers and structures to build a graph representation for the VS Code Debug Visualizer, enabling external pointer display and more extensible visualization.

Update launch configurations to load the script and to disable array/string truncation (needed for the visualizer JSON). Add a debugAdapterConfigurations entry in settings.json to use the expression template $debug_graph(${expr}) for the cppdbg adapter.
2026-07-09 12:14:27 -04:00

115 lines
4.3 KiB
Python
Executable File

#!/usr/bin/env python3
"""Drives both the C++ and Rust debug builds under gdb to their equivalent
breakpoint (right after the 30/20/10 list is built), evaluates
$debug_graph(list) exactly as VS Code's "Debug Visualizer" extension would
(via -data-evaluate-expression), and replays the extension's own
parseEvaluationResultFromGenericDebugAdapter algorithm on the raw result --
so we can tell, without going through the VS Code UI, whether our JSON will
actually be recognized or whether the extension will fall back to its
generic byte-walk visualization.
The parsing port below mirrors:
external/vscode-debug-visualizer/extension/src/VisualizationBackend/
parseEvaluationResultFromGenericDebugAdapter.ts
Keep it in sync if that file changes upstream.
Writes debug_cpp.json / debug_rust.json into the output directory (default
~/lg, matching the style of the extension's own captured dumps): either the
resolved data object on success, or a {"PARSE_ERROR": ..., "raw": ...}
diagnostic on failure.
"""
import json
import re
import subprocess
import sys
from pathlib import Path
REPO = Path(__file__).resolve().parent.parent
def run_gdb(gdb_bin, binary, break_file, break_line):
commands = [
"-gdb-set print elements 0",
"-gdb-set print characters 0",
"source %s" % (REPO / "gdb" / "debug_graph.py"),
"-break-insert %s:%d" % (break_file, break_line),
"-exec-run",
'-data-evaluate-expression "$debug_graph(list)"',
]
proc = subprocess.run(
[gdb_bin, "--interpreter=mi", binary],
input="\n".join(commands).encode(),
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT,
timeout=15,
cwd=str(REPO),
)
out = proc.stdout.decode(errors="replace")
matches = re.findall(r'\^done,value="(.*)"\s*$', out, re.M)
errors = re.findall(r'\^error,msg="(.*)"\s*$', out, re.M)
if not matches:
raise RuntimeError("no ^done,value=... in gdb output; errors=%r\n---\n%s" % (errors, out))
return matches[-1]
def is_enclosed_with(s, ch):
return s.startswith(ch) and s.endswith(ch) and len(s) >= 2
def parse_like_extension(mi_escaped_value):
"""Port of parseEvaluationResultFromGenericDebugAdapter, applied to the
raw MI `value="..."` payload (itself one layer of MI's own
string-escaping around whatever gdb's evaluate actually reported)."""
result_text = json.loads('"' + mi_escaped_value + '"') # undo MI's escaping
json_data = result_text.strip()
try:
try:
if is_enclosed_with(json_data, '"') or is_enclosed_with(json_data, "'"):
json_data2 = json_data[1:-1]
else:
json_data2 = json_data
result_obj = json.loads(json_data2)
except Exception:
# "in case of C++": the whole thing is itself a JSON string
# literal; unwrap it once, then parse *that* as JSON.
s = json.loads(json_data)
result_obj = json.loads(s)
return {"ok": True, "data": result_obj}
except Exception as e:
return {"ok": False, "error": str(e), "raw": result_text}
def dump(label, gdb_bin, binary, break_file, break_line, out_dir):
try:
raw_value = run_gdb(gdb_bin, binary, break_file, break_line)
except Exception as e:
result = {"PARSE_ERROR": "gdb invocation failed", "detail": str(e)}
else:
parsed = parse_like_extension(raw_value)
if parsed["ok"]:
result = parsed["data"]
else:
result = {
"PARSE_ERROR": parsed["error"],
"raw": parsed["raw"],
"note": "This is what the Debug Visualizer extension would fail to parse, "
"triggering its generic byte-walk fallback (constructGraphFromVariablesReference).",
}
out_path = out_dir / ("debug_%s.json" % label)
out_path.write_text(json.dumps(result, indent=4))
print("Wrote %s (%s)" % (out_path, "OK" if "PARSE_ERROR" not in result else "PARSE_ERROR"))
def main():
out_dir = Path(sys.argv[1]) if len(sys.argv) > 1 else Path.home() / "lg"
out_dir.mkdir(parents=True, exist_ok=True)
dump("cpp", "gdb", str(REPO / "cpp" / "list_example_cpp"), "cpp/main.cpp", 66, out_dir)
dump("rust", "rust-gdb", str(REPO / "target" / "debug" / "list_example"), "src/main.rs", 51, out_dir)
if __name__ == "__main__":
main()