gdb Debugger

How to Repeat Until Errors using GDB or LLDB Debugger

When debugging programs, it’s common to want to repeatedly run a program until it encounters an error. Both GDB (GNU Debugger) and LLDB (LLVM Debugger) offer ways to automate this process. Let’s dive into how to set this up in each debugger.

This is particular very useful to debug the flakey programs e.g. some tests when the tests may fail randomly or rarely crashed with SegFault e.g. Segmentation fault (or Bus Error).

Introduction: GDB vs LLDB

GDB (GNU Debugger) and LLDB (LLVM Debugger) are powerful tools for debugging applications at a low level. GDB is traditionally used with programs compiled by GCC, while LLDB is part of the LLVM project and works seamlessly with Clang. Both offer robust features, but GDB is more commonly used in Linux environments, while LLDB is favored on macOS and when working with Swift.

Automating Execution Until Error

Debugging repetitive tasks can be tedious. Automating these tasks to run until an error occurs can save time and effort. Here’s how you can set up both GDB and LLDB to repeat execution until an error is encountered.

GDB Script

Below is a GDB script that repeats execution until an error occurs:

repeat_until_error.gdb

while 1
  run
  if $_exitcode != 0
    echo "Error occurred with exit code: $_exitcode\n"
    break
  end
end

To run this script, save it as repeat_until_error.gdb and execute GDB with:

gdb -q -x repeat_until_error.gdb ./your_program

Alternatively, when you are at gdb prompt, run:

source repeat_until_error.gdb

The “run” launches the program, you could add parameters to it, for example:

run param1 param2 ...

You could use “r” short for “run”.

LLDB Script

Similarly, in LLDB, you can achieve the same with this script:

repeat_until_error.lldb

while (1)
  run
  process launch
  if (process status != 0)
    script print("Error occurred with exit code:", lldb.process.GetExitStatus())
    break
  end
end

To run this script, save it as repeat_until_error.lldb and run:

lldb --source repeat_until_error.lldb ./your_program

Alternatively, at the lldb prompt, run:

source repeat_until_error.lldb

After the command “run”, you could launch your program with additiona parameters such as:

run param1 param2

Conclusion

Both GDB and LLDB offer convenient ways to automate debugging tasks, and the choice between the two often comes down to the platform and toolchain you’re working with. GDB’s integration with GCC makes it a go-to for Linux developers, while LLDB’s seamless use with Clang and macOS makes it equally powerful.

Automating repetitive debugging commands can save you a lot of time and effort — whether you’re using GDB or LLDB, these scripts can help streamline your workflow.

gdb, lldb Debugger

• How to Repeat Until Errors using GDB or LLDB Debugger?

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