Copy Cpp Debug Variable Extension

A VS Code extension that recursively expands a C/C++ debug variable (or Watch expression) and copies the result as JSON to the clipboard, or saves it to a file.

It talks directly to the active Debug Adapter via the Debug Adapter Protocol (DAP), so it works with any C/C++ adapter that exposes a variablesReference — cppdbg, lldb-vscode, clangd, and friends. It does not depend on the DOM of the Variables view.

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Features

• Copy / Save from the Variables & Watch context menu — right-click any node in the Run and Debug view to copy or save it as JSON. No expression needed; the menu passes the node directly.
• Copy / Save via a command — Copy Debug Variable as JSON and Save Debug Variable as JSON prompt for a Watch expression (person, vec[0], myObject.field, …) and read the variable tree.
• Recursive expansion — follows variablesReference to descend into structs, classes, arrays, pointers, and STL containers.
• String-aware leaf handling — std::string, std::u8string, std::wstring, std::u16string, std::u32string, std::string_view, std::pmr::*, ABI-tagged std::__cxx11::basic_string<…> / std::__1::basic_string<…>, const char *, char[N], wchar_t *, std::byte[N] / std::byte * (e.g. PMR back-buffer), etc. are treated as leaves. The leaf value is, in priority order: "" for an empty container (indexedItems === 0); the full UTF-8 / UTF-16 text reconstructed from char / byte children when the adapter exposes them; bytes decoded as UTF-8 when the adapter drops a cppvsdbg byte dump (0x… {NN '?', …, …}) into value (covers std::byte[N] / std::byte * when no children are exposed); nothing when the adapter only exposes a truncated preview. No internal [size] / [capacity] / [allocator] leakage either way.
• Safety limits — maxDepth, maxVariables, maxArrayItems, and variablePagingSize cap recursion so a misclick never freezes the host.
• Multi-session support — the context-menu path resolves the correct DebugSession from the sessionId passed by VS Code, so concurrent debug sessions don't cross-talk.
• Result document — output JSON wraps the variable tree with schemaVersion, source (variables / watch), expression, sessionType, capturedAt, warnings, truncated, and nodeCount metadata.

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Commands

Command ID	Title	Entry point
copy-cpp-debug-variable.copyAsJson	Copy Debug Variable as JSON	Command Palette — prompts for an expression
copy-cpp-debug-variable.saveAsJson	Save Debug Variable as JSON	Command Palette — prompts for an expression, then a save dialog
copy-cpp-debug-variable.copySelectedAsJson	Copy as JSON	Right-click menu inVariables and Watch
copy-cpp-debug-variable.saveSelectedAsJson	Save as JSON	Right-click menu inVariables and Watch

The two menu commands are intentionally hidden from the Command Palette (menus.commandPalette → when: false) — without a context argument they fall back to the input-box flow, and exposing both entry points would be redundant.

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Requirements

• VS Code ^1.125.0 (see engines.vscode in package.json).
• A C/C++ debug adapter that supports the standard DAP requests (evaluate, variables). The extension is adapter-agnostic; cppdbg is the primary target.

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Extension Settings

This extension contributes the following settings (under copy-cpp-debug-variable.*):

Setting	Default	Min	Description
maxDepth	8	1	Maximum recursion depth when expanding variables.
maxVariables	10000	1	Maximum total number of variable nodes to read.
maxArrayItems	1000	1	Maximum array / vector elements to enumerate.
variablePagingSize	100	1 — 1000	Page size for DAPvariables requests.

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Usage

1. From the Variables / Watch context menu (recommended)

1. Start a debug session and pause at a breakpoint.
2. In the Variables or Watch view, right-click any variable.
3. Choose Copy as JSON or Save as JSON.
4. The result lands in the clipboard (or a file you pick). A status bar message reports the node count.

2. From the Command Palette

1. Start a debug session and pause at a breakpoint.
2. Open the Command Palette and run Copy Debug Variable as JSON (or Save Debug Variable as JSON).
3. Type a C/C++ expression — for example people, people[0].address, company.employees, linked->next.
4. The result is copied to the clipboard (or saved to a file you pick).

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Try it locally

A runnable C++23 sample lives in demo/. Build it with CMake, drop a breakpoint after people is initialised, and exercise the commands against the suggested expressions (people, people[0], people[0].address, people[0].scores, company, company.employees, linked, linked->next).

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Known Issues

• Some adapters do not expose variablesReference for primitive locals. In that case the leaf value is still captured, but no children will be fetched.
• Adapters that do not surface individual char children for string-like types will fall back to the adapter's display value rather than a reconstructed text.
• Expressions that depend on registers or hardware state may be rejected by the adapter; failures surface as a notification and a warnings entry in the result document.

Release Notes

See CHANGELOG.md for the full history.

License

MIT — © xmmmmmovo