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DTD

This is the repository for paper "DTD: Comprehensive and Scalable Testing for Debuggers"

Bugs we've found

Please go to our google site for a complete list of bugs we've found in GDB/LLDB.

Motivating example

The following is an example C program that triggers a bug in GDB. This bug occurs when the source is compiled using GCC. We observe this in O1,O2,O3, even O0, hooray), meaning this is a debugger bug instead of a compiler bug (which previous works focuses on). DTD is very good at locating such bugs.

int a = 1;
int func() {
    int i;
    for (; i < 1; i++);
    if (a) {
        short b = 2; /* error point */
        { int i; }
    }
}
int main() { func(); }

Just run demo.sh to see how DTD detect and report this bug.

./demo.sh

Here is the expected output.

On line 6: LLDB: i = 1, GDB: i = opted

It says that, on line 6, LLDB saw an variable i with value 1, but GDB saw i has been optimized. Therefore, there is a bug in GDB causing i gone missing or a bug in LLDB causing a spurious i to appear.

File list

  • comparator.py: Compare two traces and yield their differences.
  • gdb_script.py: GDB interpreted python script to generate "debugger trace" of a binary.
  • lldb_script.py: LLDB interpreted python script to generate "debugger trace" of a binary.
  • step_generator.py: Heuristically generate which steps to collect complete debugger trace.
  • trace_diff.py: Utility python script for trace diff.