rr – record and replay debugger for C/C++
RR is a C/C++ debugging tool for Linux, enhancing gdb by enabling deterministic recording and replay of failures, supporting various applications like Firefox, with low overhead and a chaos mode.
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The tool RR aims to be a primary C/C++ debugging tool for Linux, enhancing gdb by allowing users to record failures once and then debug the recording deterministically as many times as needed. It offers efficient reverse execution under gdb, supports various applications, including Firefox and Chrome, and enables debugging of multiple-process workloads. RR features low overhead, durable traces, and a chaos mode to reproduce intermittent bugs. Developers can use RR to record, replay, and debug applications efficiently. The tool's deterministic replay preserves execution details, making debugging easier and more effective. RR's design goals include simplicity, deployability on stock Linux kernels, and low runtime overload. While RR has limitations like emulating a single-core machine and requiring knowledge of system calls, it provides a valuable solution for debugging complex applications like Firefox. Overall, RR lowers the cost of fixing bugs, improves software quality, and enhances the debugging experience for developers.
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- Users find RR invaluable for debugging complex C/C++ issues, especially with features like deterministic replay and reverse execution.
- There are discussions about RR's compatibility with other languages and environments, including Rust, OpenGL, Vulkan, and even Android.
- Some users mention alternative tools and methods, such as GDB's built-in reverse debugging and WinDbg for Windows.
- RR's limitations are noted, particularly with concurrency bugs and specific hardware like Ryzen CPUs.
- There is interest in integrating RR more seamlessly into development workflows and exploring its potential for kernel debugging.
18 commentsMy limited understanding says a debugger needs: a list of symbols (.pdb files on windows, can't remember what they are on linux), understanding of syscalls and a few other similar things. I thought they don't care too much what generated the binaries they are debugging (obviously as long as it's native code).
Doesn't rr work with other languages like rust, zig, odin, nim, and similar ones? Obviously, I wouldn't expect it to work for python, js, c# and other languages with managed memory.
Despite that, it would be very, very, very cool if some languages built rr directly into their tooling. Obviously you can always "just" use rr/gdb, but imagine if rr invocations were as easy to set up and do as pdb is in Python!
> [...] just click on the incorrect value. With full program history Pernosco can immediately explain where this value came from. The value is tracked backwards through events such as memcpys or moves in and out of registers until we reach a point where the value "originated" from, and each step in this process is displayed in the "Dataflow" panel that opens automatically. There is no need to read or understand the code and think about what might have happened, we can simply ask the debugger what did happen.
I assume rr provides more features and flexibility. Anyway I want to mention that GDB itself can already reverse debug for some time now.
https://www.forrestthewoods.com/blog/windbg-time-travelling-...
https://news.ycombinator.com/item?id=31617600 (June 2022)
Super useful, especially considering I know barely anything about x86-64.
rr record /tmp/Debug/bin/llvm-mc a.s && rr replay -d cgdb
I've have success story with some bugs only reproducible with LTO. Without rr it would be a significant challenge.
It would be nice if Linux kernel could be debugged with rr. Does anyone have success with kernel under rr+qemu ? :)
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