smldbg

A small, educational debugger with no dependencies.

Prerequisites

To build the project and run the tests, the following are required:

• A C++20 compliant compiler (tested with clang++ 11.0.0 and g++ 10.2.0)
• CMake 3.12 or higher
• The Google Test Framework

Building the Project

git checkout git@github.com:progbits/smldbg
cd smldbg
mkdir build && cd build
cmake ..
make

Running the Debugger

To run the debugger, compile the following small example program with optimization disabled and debug symbols enabled (normally flags -o0 and -g for most compilers).

#include <iostream>

void qux(int value) {
  std::cout << "value: " << value << "\n";
}

void baz(int value) {
  qux(value + 3);
}

void bar(int value) {
  baz(value + 2);
}

void foo(int value) {
  bar(value + 1);
}

int main() {
  foo(1);
  bar(3);
  return 0;
}

The following commands will step through the program, set breakpoints on both methods and source code locations and inspect the current program state.

start               # Start debugging the executable
step 2              # Move the instruction pointer forwards 2 instructions
info registers      # Print the current register values
bt                  # Print the backtrace of the current stack
break main.cpp:12   # Add a new breakpoint at line 12
cont                # Run until the next breakpoint is hit
bt                  # Print the backtrace of the current stack
print value         # Print the variable `value`
break qux           # Set a breakpoint on the function `qux(...)`
cont                # Run until the next breakpoint is hit
bt                  # Print the backtrace of the current stack
print value         # Print the variable `value`
set value 99        # Set the variable `value` to 99
step                # Move the instruction pointer forwards 1 instruction
finish              # Run until the end of the current method
finish              # Run until the end of the current method
bt                  # Print the backtrace of the current stack
finish              # Run until the end of the current method
finish              # Run until the end of the current method
delete              # Delete all breakpoint
next                # Run until the next line
step                # Move the instruction pointer forwards 1 instruction