dbg(…)

A macro for printf-style debugging fans.

Debuggers are great. But sometimes you just don't have the time and nerve to set up everything correctly and just want a quick way to inspect some values at runtime.

This projects provides a single header file (dbg.h) that defines a dbg(…) macro which can be used in all circumstances where you would typically write printf("…", …) or std::cout << … << std::endl; yet another time.

Examples

#include <dbg.h>

int main() {
  std::string message = "hello";
  dbg(message);  // [DEBUG example.cpp:5 (main)] message = "hello"

  const int a = 2;
  const int b = dbg(3 * a) + 1;  // [DEBUG example.cpp:8 (main)] 3 * a = 6

  std::vector<int> numbers{b, 13, 42};
  dbg(numbers);  // [DEBUG example.cpp:11 (main)] numbers = {7, 13, 42} (size: 3)

  dbg("this line is executed");  // [DEBUG example.cpp:13 (main)] this line is executed

  dbg(sizeof(int));  // [DEBUG example.cpp:15 (main)] sizeof(int) = 4

  return 0;
}

// Use it inside expressions:
int factorial(int n) {
   if (dbg(n <= 1)) {
       return dbg(1);
   } else {
       return dbg(n * factorial(n - 1));
   }
}

// A call to factorial(4) prints:
// [DEBUG factorial.cpp:9 (factorial)] n <= 1 = false
// [DEBUG factorial.cpp:9 (factorial)] n <= 1 = false
// [DEBUG factorial.cpp:9 (factorial)] n <= 1 = false
// [DEBUG factorial.cpp:9 (factorial)] n <= 1 = true
// [DEBUG factorial.cpp:10 (factorial)] 1 = 1
// [DEBUG factorial.cpp:12 (factorial)] n * factorial(n - 1) = 2
// [DEBUG factorial.cpp:12 (factorial)] n * factorial(n - 1) = 6
// [DEBUG factorial.cpp:12 (factorial)] n * factorial(n - 1) = 24

Features

• Prints file name, line number, function name and the original expression
• Easy to read, colorized output
• Can be used inside normal expressions
• The dbg.h header issues a compiler warning when included
• Works for containers

Installation

To make this actually useful, the dbg.h header has to be available from all kinds of different places and in all kinds of environments. The quick & dirty way is to actually copy the header file to /usr/include or to clone the repository and symlink dbg.h to /usr/include/dbg.h.

git clone https://github.com/sharkdp/dbg-macro
sudo ln -s $(readlink -f dbg-macro/dbg.h) /usr/include/dbg.h

Ideally, if this turns out to be a good idea, we would ship packages for various distributions so you don't have to make untracked changes to your filesystem.

Acknowledgement

This project is inspired by Rusts dbg!(…) macro.