The RAD Debugger Project

NOTE: This README does not document usage instructions and tips for the debugger itself, and is intended as a technical overview of the project. The debugger's README, which includes usage instructions and tips, can be found packaged along with debugger releases, or within the build folder after a local copy has been built. You can find pre-built release binaries here.

The RAD Debugger is a native, user-mode, multi-process, graphical debugger. It currently only supports local-machine Windows x64 debugging with PDBs, with plans to expand and port in the future. In the future we'll expand to also support native Linux debugging and DWARF debug info.

The debugger is currently in ALPHA. In order to get the debugger bullet-proof, it'd greatly help out if you submitted the issues you find here, along with any information you can gather, like dump files (along with the build you used), instructions to reproduce, test executables, and so on.

In addition to the debugger, we aim to further improve the toolchain with two additional related technologies: (1) the RAD Debug Info (RDI) format, and (2) the RAD Linker.

The RAD Debug Info (RDI) Format

The RAD Debug Info (RDI) format is our custom debug information format, which the debugger parses and uses, rather than the debug information natively produced by toolchains, like PDB or DWARF. To work with these existing toolchains, we convert PDB (and eventually PE/ELF files with embedded DWARF) into the RDI format on-demand.

The RDI format is currently specified in code, in the files within the src/lib_rdi folder. In rdi.h and rdi.c, the types and functions which define the format itself are specified. In rdi_parse.h and rdi_parse.c, helpers for parsing the format are included.

We also have an in-progress library for constructing and serializing RDI data, located within the src/lib_rdi_make folder.

Our radbin utility (accessible through the debugger too, via the --bin command line argument) is capable of converting native debug information formats to RDI, and of producing textual dumps of contents stored within RDI files.

The RAD Linker

The RAD Linker is a new performance linker for generating x64 PE/COFF binaries. It is designed to be very fast when creating gigantic executables. It generates standard PDB files for debugging, but it can also (optionally) natively create RAD Debug Info too, which is useful both to eliminate on-demand conversion time when debugging, but also for huge executables that otherwise create broken PDBs that overflow internal 32-bit tables.

The RAD Linker is primarily optimized to handle huge linking projects. In our test cases (where debug info is multiple gigabytes), we see 50% faster link times.

The command line syntax is fully compatible with MSVC; you can get a full list of implemented switches from /help.

Our current designed-for use case for the linker is to help with the compile-debug cycle of huge projects. We don't yet have support for link-time-optimizations, but this feature is on the road map.

By default, the linker spawns as many threads as there are cores, so if you plan to run multiple linkers in parallel, you can limit the number of thread workers via /rad_workers.

We also have support for large memory pages, which, when enabled, reduce link time by another 25%. To link with large pages, you need to explicitly request them via /rad_large_pages. Large pages are off by default, since Windows support for large pages is a bit buggy; we recommend they only be used in Docker or VM images where the environment is reset after each link. In a standard Windows environment, using large pages otherwise will fragment memory quickly, forcing a reboot. We are working on a Linux port of the linker that will be able to build with large pages robustly.

A benchmark of the linker's performance is below:

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Project Development Setup Instructions

NOTE: Currently, only x64 Windows development is supported for the project.

1. Installing the Required Tools (MSVC & Windows SDK)

In order to work with the codebase, you'll need the Microsoft C/C++ Build Tools v15 (2017) or later, for both the Windows SDK and the MSVC compiler and linker.

If the Windows SDK is installed (e.g. via installation of the Microsoft C/C++ Build Tools), you may also build with Clang.

2. Build Environment Setup

Building the codebase can be done in a terminal which is equipped with the ability to call either MSVC or Clang from command line.

This is generally done by calling vcvarsall.bat x64, which is included in the Microsoft C/C++ Build Tools. This script is automatically called by the x64 Native Tools Command Prompt for VS <year> variant of the vanilla cmd.exe. If you've installed the build tools, this command prompt may be easily located by searching for Native from the Windows Start Menu search.

You can ensure that the MSVC compiler is accessible from your command line by running:

cl

If everything is set up correctly, you should have output very similar to the following:

Microsoft (R) C/C++ Optimizing Compiler Version 19.29.30151 for x64
Copyright (C) Microsoft Corporation.  All rights reserved.

usage: cl [ option... ] filename... [ /link linkoption... ]

3. Building

Within this terminal, cd to the root directory of the codebase, and just run the build.bat script:

build

You should see the following output:

[debug mode]
[msvc compile]
[default mode, assuming `raddbg` build]
metagen_main.c
searching C:\devel\raddebugger/src... 458 files found
parsing metadesk... 16 metadesk files parsed
gathering tables... 97 tables found
generating layer code...
raddbg_main.c

If everything worked correctly, there will be a build folder in the root level of the codebase, and it will contain a freshly-built raddbg.exe.

This raddbg.exe will have been built in debug mode, which is not built with optimizations, and may perform worse. To produce a release mode executable, run build.bat with a release argument:

build release

This build will take significantly longer.

By default, build.bat only builds the debugger if no arguments (or just release) are passed, but additional arguments can be passed to build the RAD Linker, or the radbin CLI binary file utility:

build radlink release
build radbin release

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Project Roadmap

The Initial Alpha Battle-Testing Phase

The first priority for the project is to ensure that the most crucial components are functioning extremely reliably for local, x64, Windows development. For the debugger, this would include parts like debug info conversion, debug info loading, process control, stepping, evaluation (correct usage of both location info and type info), and a robust frontend which ensures the lower level parts are usable. For the linker, this is a matter of reliability and convergence with existing linker behavior.

We feel that we've already come a long way in all of these respects, but given the massive set of possible combinations of languages, build settings, toolchains, used language features, and patterns of generated code, we still expect some issues, and are prioritizing these issues being resolved first.

We also hope to continue to improve performance in this phase. For the debugger, this primarily includes frontend performance, introducing caches when economical to do so, and tightening existing systems up. For the linker, it has been mostly tuned thus far for giant projects, and so we'd like to improve linking speed for small-to-mid sized projects as well.

For the linker, there are also a number of features to come, like dead-code-elimination (/opt:ref), and link-time-optimizations with the help of clang (we won't support LTCG from MSVC, since it is undocumented).

Local x64 Linux Debugging Phase

The next priority for the project is to take the rock solid x64 Windows debugging experience, and port all of the relevant pieces to support local x64 Linux debugging also.

The debugger has been written to abstract over the parts that need to differ on either Linux or Windows, and this is mainly going to be a task in building out different backends for those abstraction layers.

The major parts of this phase are:

• Porting the src/demon layer to implement the Demon local process control abstraction API.
• Implementing an x64 ELF Linux unwinder in the src/ctrl layer.
• Creating a DWARF-to-RDI converter (in the same way that we've built a PDB-to-RDI converter). A partial implementation of this is in src/rdi_from_dwarf.
• Porting the src/render layer to implement all of the rendering features the frontend needs on a Linux-compatible API (the backend used on Windows is D3D11).
• Porting the src/font_provider layer to a Linux-compatible font rasterization backend, like FreeType (the backend used on Windows is DirectWrite).
• Porting the src/os layers to Linux. This includes core operating system abstraction (virtual memory allocation, threading and synchronization primitives, and so on), and graphical operating system abstraction (windows, input events, and so on).

Once the above list is complete, and once every part is rock solid, the Windows debugging experience we'll have w