Debugging

From UFO:AI

Contents 1 General 2 Windows 2.1 Code::Blocks 2.2 Dr.MinGW 2.3 gdb on Windows 3 Linux 3.1 gdb 3.1.1 Generate core dumps 3.1.2 Breakpoints 3.1.3 Inspect variables 3.1.4 Other useful commands 3.2 valgrind 3.3 bugle 4 Useful gdb stuff 4.1 Hints 4.2 Commands 4.3 Links

General

See also Coding/Debug commands.

Windows

Code::Blocks

• Compile the game in debugging mode
  • To add debugging symbols in Windows use in C::B the Build target, through the build menu:

    windows_debug

    instead of

    windows

• The Code::Blocks-installation includes gdb.
• Integrated debugging
  • Use +set vid_fullscreen 0 +set vid_grabmouse 0 +set developer 1 as program arguments
  • Just select the debugging option from the menu - you will get a backtrace and so on after the game crashed
• Manual debugging
  • You should add the Code::Blocks installation folder to your environment path variable (most likely C:\Code::Blocks\bin)
  • To start UFO:AI in the debugger you need to enter the windows-console (Start->Execute->cmd.exe)
  • Enter the UFO:AI folder and type

    gdb ufo.exe

  • Now you are in the debug console of gdb
  • Run the game with

    • run +set vid_fullscreen 0 +set vid_grabmouse 0

    • or with

      run +set vid_fullscreen 0 +set vid_grabmouse 0 +set developer 1

      if you need the debug-messages from within the code.
  • After a crash you can toggle via Alt Tab to gdb console.
  • To locate the problem, type

    bt full

    which generate a backtrace and display the values of local variables.
• Submit theses informations to the bugtracker.

Dr.MinGW

Dr.MinGW is a JIT debugger (Just-In-Time-Debugger) - see the homepage for more information about it.

gdb on Windows

Yes, gdb also works under Windows. The usage is teh same as shown in the #Linux and #Useful gdb stuff section below.

Add instructions here on how to make gdb work. It seems to be incldued in Dev-Cpp, but not in others - and even in Dev-Cpp you need to set paths.

Linux

gdb

• You have to have gdb installed.
• Compile the game in debugging mode (standard).
• Go to directory where ufo binary is located (see directory tree).
• Run

  gdb ufo

  from the commandline.
• Now you are in the debug console of gdb
• Run the game with

  • run +set vid_fullscreen 0 +set vid_grabmouse 0

  • or with

    run +set vid_fullscreen 0 +set vid_grabmouse 0 +set developer 1

    if you need the debug-messages from within the code.
• After a crash you can toggle via 'Alt Tab to gdb console.
• Type

  bt full

  to generate a backtrace and locate the problem.
• Submit theses informations to the bugtracker.

Visit this site for a more in-depth gdb tutorial.

Generate core dumps

You can also generate core dumps from a running process - attach gdb to the process, type generate-core-file and detach again. Now you have the core file for later debugging.

Breakpoints

There are several commands to set breakpoints via gdb:

• break function
• break filename:line

To remove them type:

• clear function
• clear filename:line
• delete

Remove all breakpoints

• delete n

Remove the ith breakpoint

Type info breakpoints to get a list of all breakpoints

Inspect variables

You can use print i or the abbrevation p i to print the content of the variable i. You can also print structures by typing ptype structureName_t.

print accepts some format parameters:

• o = octal
• x = hex
• d = decimal
• u = unsigned decimal
• t = binary
• f = float
• a = address
• c = char

Use them via print /x i

Other useful commands

• To find out where you currently are type the command: where
• To print some source around the current location type: list
• step Execute a single line in the program. If the current statement calls a function, the function is single stepped.
• next Execute a single line in the program but treat function calls as a single line. This command is used to skip over function calls.

valgrind

Use valgrind to detect and fix memory bugs.

bugle

bugle can be used to trace OpenGL calls, hunt for unchecked OpenGL errors, take video shots, and do plenty of other OpenGL-related debugging.

e.g. to get a full trace of OpenGL calls:

BUGLE_CHAIN=trace LD_PRELOAD=/path/to/libbugle.so ufo +set gl_driver /path/to/libbugle.so

Useful gdb stuff

Hints

• Use tab for command and variable completion
• Ctrl C stops the program (use c or continue to continue the execution

Commands

help [command]

Prints information about the gdb command

list

Prints code from current active position (useful to set breakpoints)

break

Handle breakpoints. Type help breakpoints to gdb console to get information. Example: break 184 if (status == 0)

b CL_ParticleRun2 will e.g. set a breakpoint to the function CL_ParticleRun2

watch

Sets a watchpoint. The main difference between watch and breakpoints is that a breakpoint was set for a specific line - and a watchpoint can get active on every line - it only needs it's condition to get true. Example: watch (varname > 1024)

inspect

Prints the value of a variable to gdb console (see print)

print

Prints a value of a variable to gdb console (see inspect). If variable is a pointer you can dereferencing it by typing print *[varname] - like in C. You can even assign a value to a var by typing print [varname] = [value]

ptype

Prints the type (typedef or struct) of the given variable name

bt

Prints the backtrace

c

Continue the game execution

Links

• GDB documentation