Programming Cleverness Roundtable (Friday)

Debugging

• Win32 has a WriteDump that can create a 50k "minidump" of a thread built with debug info from VC7. Can then inspect state with debugger. Used, eg. with a button in the assert dialog.
• Stack trace + custom memory manager + debug info can be used to automatically find memory leaks.
• B.net servers send email to programmers.
• Database to map function names to programmer: e-mail the right person with an assert.
• Watch dog thread that looks for keys pressed for > 4 seconds: used to dump a minidump, int 3, or exit game.
• If you turn off a particular optimization (didn't catch which one), you can do your own stack walk without dbghlp.
• Visual debugging gives a big payoff:
  • Visualize cues that could start sounds
  • bright pink for missing textures
  • print out a text string for missing sound (contains more useful info than replacing with a sine wave)
• Use code to make conditional breakpoints, often faster than using debugger facilities
• Script function to trigger debugger breakpoint.

Big logs

• Problem: logging / warnings event queue fills up or gets too much data to be useful.
• Can send to screen to make sure it gets fixed...
• Disable/enable logging on a per class basis; use a string prefix to help filtering
• VC7's __FUNCTION__ preprocessor symbol very handy.
• Could prioritize asserts: eventually never trip any.
• Use a per-user profiles stored on HD to map type of error and severity to action (assert, log, ignore).

Custom Memory Management

• Memory poisoning in custom memory allocation very good: init memory to known values, guards at ends, change when deallocated. Try Paul Nettle's mmgr.
• Can measure the amount of wasted space: that which was never changed from init value.
• Can limit total memory.
• Can test a pointer to see if it points into allocated space. Similar to ATL/MS debug libraries that have "is good {read,write} ptr"

Misc

• Daily build errors mailed to every programmer.
• Netscape used talkback system, or get minidumps from Microsoft.
• Output screenshots to make movies
• To get instant replays to work, add function traces so you can locate divergences
• Nice to be able to pause AI and physics but still render and toggle various debug visualizations.
• Keyboard lights may be used as debug output when you have nothing else.
• Silly: using perfect pitch for debug output and profiling
• Avoid catch(...)
• On linux: valgrind recommended
• Crash only in release mode: non-initialized memory, or asserts with side effects
• SoftIce on Win9X can do conditional breakpoints
• Look at Visual Assist for use with VC++, though bad with lots of templates or very large projects.
• Take advantage of scripting in editor to add a new class to the project with dummy test code.
• These and other VC++ tricks in "Debugging Applications" by Jon Robbins:
  • Look at autoexp.dat: for viewing data in debugger.
  • @err shows GetLastErr
  • f() calls function f in watch window (but calls it twice! beware)
  • @clk give time stamp
  • ,su for unicode string
  • ,hr for hresult
• There is some registry key for avoiding pause when using direct input.
• f12 breaks into debugger in VC++, can't be remapped
• debug SDK: can use MS's debug data server to debug breaks into GDI32, etc.
• "ReadDirectoryChangesW" fuction so artists can drop a bitmap (or whatever) into a directory and it immediately appears in the game
• PC-Lint good for giving warnings
• pragma 4389 handy for something or other.