Printing debug information

Very often programmers put print statements purely for the sake of debugging.

This is annoying when running the final program

where this information should not be needed any more.

One easy way out of the dilemma is given by the C preprocessor:

#define DEBUG 1

#ifdef DEBUG

p rintf(“printing some variable contents %d\n”,variable);

#endif

Commenting out the #define statement will get rid of all debugging prints.

The debugger gdb

Sometimes printing debug information is not enough

and we have to use a debugger.

gdb the GNU debugger is still the standard tool

Compile your program with the -g option to retain the symbol table

Then run the program within the debugger

gdb yourProgram

Using gdb

• break: set a breakpoint to stop running when arriving at this point
• run: start the program
• continue: continue running after a breakpoint
• next: execute the program line next line
• step: step into the function if the next line is a function call
• list: print the source code at the current position in the program
• bt: backtrace, show the program stack
• print: print a variable

This is rather short (a bit more than 800 pages)