EpicGames/raddebugger

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: ---

Project Development Setup / Local Build Instructions

The project is actively developed both on Windows x64 and Linux x64 development machines. Click on whichever you'd like to use.

Windows x64

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

First, you'll need the Microsoft C/C++ Build Tools v15 (2017) or later, for 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 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 ```

Linux x64

1. Installing the Required Tools (GCC or Clang, Libraries)

First, you'll need either GCC or Clang, if you don't already have them. They can be obtained by running one of the following commands, depending on your toolchain of choice and distribution:

GCC on Ubuntu / Debian / Mint

``` sudo apt update && sudo apt install build-essential ```

Clang on Ubuntu / Debian / Mint

``` sudo apt update && sudo apt install clang llvm ```

GCC on Arch / Manjaro

``` sudo pacman -S base-devel ```

Clang on Arch / Manjaro

``` sudo pacman -S clang llvm ``` If you've installed the Clang and LLVM tooling required, you can run: ``` clang --version && llvm-ar --version ``` You should see output similar to the following: ``` Ubuntu clang version 18.1.3 (1ubuntu1) Target: x86_64-pc-linux-gnu Thread model: posix InstalledDir: /usr/bin Ubuntu LLVM version 18.1.3 Optimized build. ``` If you've installed the GCC tooling required, you can run: ``` gcc --version && gcc-ar --version ``` You should see output similar to the following: ``` gcc (Ubuntu 13.3.0-6ubuntu2~24.04.1) 13.3.0 Copyright (C) 2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. GNU ar (GNU Binutils for Ubuntu) 2.42 Copyright (C) 2024 Free Software Foundation, Inc. This program is free software; you may redistribute it under the terms of the GNU General Public License version 3 or (at your option) any later version. This program has absolutely no warranty. ```

2. Installing Dependencies

The debugger project relies on a few dynamically linked libraries being present on the system:

• libfreetype
• libx11
• libxext
• libxfixes
• libxrandr
• libgl
• libegl

You'll need the development packages for them in order to build. These can be installed using one of the following commands, depending on your distribution:

Ubuntu / Debian / Mint

``` sudo apt install -y libfreetype6-dev libx11-dev libxext-dev libxfixes-dev libxrandr-dev libgl-dev libegl-dev ```

Arch / Manjaro

``` sudo pacman -S --needed freetype2 libx11 libxext libxfixes libxrandr libglvnd ```

3. Building

To build, cd to the root directory of the codebase, and run the build.sh script: ``` ./build.sh ``` You should see something similar to the following output: ``` [clang compile] [debug mode] [building metagen] searching /mnt/c/devel/raddebugger/src... 562 files found parsing metadesk... 23 metadesk files parsed gathering tables... 138 tables found generating layer code... ``` 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 binary. This raddbg 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.sh with a release argument: ``` ./build.sh release ``` This build will take significantly longer. By default, build.sh 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.sh radlink release ./build.sh radbin release ``` ---

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 worked diligently to create will also be available natively on Linux machines.

And Beyond!

There are several directions we might take after these two major phases, like remote debugging, porting to different architectures, further improving the debugger's features (like improving the visualization engine), and so on. But for now, we're mostly focused on those first two phases. ---

Codebase Introduction

Top-Level Directory Descriptions

• data: Small binary files which are used when building, either to embed

within build artifacts, or to package with them.

• src: All source code.

After setting up the codebase and building, the following directories will also exist:

• build: All build artifacts. Not checked in to version control.
• local: Local files, used for local build configuration input files. Not

checked in to version control.

Layer Descriptions

The codebase is organized into layers. Layers are separated either to isolate certain problems, and to allow inclusion into various builds without needing to pull everything in the codebase into a build. Layers correspond with folders inside of the src directory. Sometimes, one folder inside of the src directory will include multiple sub-layers, but the structure is intended to be fairly flat. Layers correspond roughly 1-to-1 with namespaces. The term "namespaces" in this context does not refer to specific namespace language features, but rather a naming convention for C-style namespaces, which are written in the codebase as a short prefix, usually 1-3 characters, followed by an underscore. These namespaces are used such that the layer to which certain code belongs may be quickly understood by glancing at code. The namespaces are generally quite short to ensure that they aren't much of a hassle to write. Sometimes, multiple sub- layers will share a namespace. A few layers do not have a namespace, but most do. Namespaces are either all-caps or lowercase depending on the context in which they're used. For types, enum values, and some macros, they are capitalized. For functions and global variables, they are lowercase. Layers depend on other layers, but circular dependencies would break the separability and isolation utility of layers (in effect, forming one big layer), so in other words, layers are arranged into a directed acyclic graph. A few layers are built to be used completely independently from the rest of the codebase, as libraries in other codebases and projects. As such, these layers do not depend on any other layers in the codebase. The folders which contain these layers are prefixed with lib_, like lib_rdi. A list of the layers in the codebase and their associated namespaces is below:

• artifact_cache (AC_): Implements an asynchronously-filled cache of

computation artifacts, which are automatically evicted when not accessed. Used for asynchronously streaming and caching process memory and file system contents, as well as asynchronously preparing visualizer data.

• base (no namespace): Universal, codebase-wide constructs. Strings, math,

memory allocators, helper macros, command-line parsing, and so on. Requires no other codebase layers.

• codeview (CV_): Code for parsing and writing the CodeView format.
• coff (COFF_): Code for parsing and writing the COFF (Common Object File

Format) file format.

• content (C_): Implements a cache for general data blobs, keyed by a

128-bit hash of the data. Also implements a keying system on top, where keys refer to a unique identity which corresponds to a history of 128-bit hashes. Used as a general data store by other layers.

• ctrl (CTRL_): The debugger's "control system" layer. Implements

asynchronous process control, stepping, and breakpoints for all attached processes. Runs in lockstep with attached processes. When it runs, attached processes are halted. When attached processes are running, it is halted. Driven by a debugger frontend on another thread.

• dbg_engine (D_): Implements the core debugger system, without any

graphical components. This contains top-level logic for things like stepping, launching, freezing threads, mid-run breakpoint addition, some caches, and so on.

• dbg_info (DI_): Implements asynchronous debug info conversion and loading.

Maintains a cache for loaded debug info. Loads RAD Debug Info (RDI) files. Launches separate processes for on-demand conversion to the RDI format if necessary. Also provides various asynchronous operations for using debug info, like fuzzy searching across all records in loaded debug info.

• demon (DMN_): An abstraction layer for local-machine, low-level process

control. The abstraction is used to provide a common interface for process control on target platforms. Used to implement part of ctrl.

• disasm (DASM_): Implements disassembly generation, including exposing the

ability to compute and cache disassembly asynchronously.

• draw (DR_): Implements a high-level graphics drawing API for the

debugger's purposes, using the underlying render abstraction layer. Provides high-level APIs for various draw commands, but takes care of batching them, and so on.

• dwarf (DW_): Code for parsing the DWARF format.
• eh (EH_): Code for parsing the EH frame format.
• elf (ELF_): Code for parsing the ELF format.
• eval (E_): A compiler for an expression language, built for evaluation of

variables, registers, types, and more, from debugger-attached processes, debug info, debugger state, and files. Broken into several phases mostly corresponding to traditional compiler phases: lexer, parser, type-checker, IR generation, and IR evaluation.

• eval_visualization (EV_): Implements the core non-graphical evaluation

visualization engine, which can be used to visualize evaluations (provided by the eval layer) in a number of ways. Implements core data structures and transforms for watch tables.

• file_stream (FS_): Implements asynchronous file streaming, storing the

artifacts inside of the cache implemented by the content and artifact_cache layers, hot-reloading the contents of files when they change. Allows callers to map file paths to data hashes, which can then be used to obtain the file's data.

• font_cache (FNT_): Implements a cache of rasterized font data, both in

CPU-side data for text shaping, and in GPU texture atlases for rasterized glyphs. All cache information is sourced from the font_provider abstraction layer.

• font_provider (FP_): An abstraction layer for various font file decoding

and font rasterization backends.

• lib_raddbg_markup (RADDBG_): Standalone library for marking up user

programs to work with various features in the debugger. Does not depend on base, and can be independently relocated to other codebases.

• lib_rdi (RDI_): Standalone library which defines the core RDI types

and helper functions for reading and writing the RDI debug info file format. Does not depend on base, and can be independently relocated to other codebases.

• lib_rdi_make (RDIM_): Standalone library for constructing RDI debug info

data. Does not depend on base, and can be independently relocated to other codebases.

• linker (LNK_): The layer which implements the RAD Linker executable

itself.

• mdesk (MD_): Code for parsing Metadesk files (stored as .mdesk), which

is the JSON-like (technically a JSON superset) text format used for the debugger's user and project configuration files and metacode, which is parsed and used to generate code with the metagen layer.

• metagen (MG_): A metaprogram which is used to generate primarily code and

data tables. Consumes Metadesk files, stored with the extension .mdesk, and generates C code which is then included by hand-written C code. Currently, it does not analyze the codebase's hand-written C code, but in principle this is possible. This allows easier & less-error-prone management of large data tables, which are then used to produce e.g. C enums and a number of associated data tables. There are also a number of other generation features, like embedding binary files or complex multi-line strings into source code.

• msf (MSF_): Code for parsing and writing the MSF file format.
• msvc_crt (MSCRT_): Code for parsing that's specific to the MSVC CRT.
• mule (no namespace): Test executables for battle testing debugger

functionality.

• mutable_text (MTX_): Implements an asynchronously-filled-and-mutated

cache for text buffers which are mutated across time. In the debugger, this is used to implement the Output log.

• natvis (no namespace): NatVis files for type visualization of the codebase's

types in other debuggers.

• os/core (OS_): An abstraction layer providing core, non-graphical

functionality from the operating system under an abstract API, which is implemented per-target-operating-system.

• os/gfx (OS_): An abstraction layer, building on os/core, providing

graphical operating system features under an abstract API, which is implemented per-target-operating-system.

• pdb (PDB_): Code for parsing and writing the PDB file format.
• pe (PE_): Code for parsing and writing the PE (Portable Executable) file

format.

• radbin (RB_): The layer implementing the radbin binary utility

executable.

• raddbg (RD_): The layer which ties everything together for the main

graphical debugger executable. Implements the debugger's graphical frontend, all of the debugger-specific UI, the debugger executable's command line interface, and all of the built-in visualizers.

• rdi (RDI_): A layer which includes the lib_rdi layer and bundles it with

codebase-specific helpers, to easily include the library in codebase programs, and have it be integrated with codebase constructs.

• rdi_from_coff (C2R_): Code for converting information in COFF files to the

equivalent RDI data.

• rdi_from_dwarf (D2R_): In-progress code for converting DWARF to the

equivalent RDI data.

• rdi_from_elf (E2R_)): Code for converting ELF data to the equivalent RDI

data.

• rdi_from_pdb (P2R_): Code for converting P