What's Worse Than Crashing?

[Philip]

Some comments:

• You have to decide at what level your error handling mechanisms should be handled; “at every level” is a not a good answer.

• You have to decide very carefully around retry loops. http://blogs.msdn.com/oldnewthing/archive/2005/11/07/489807.aspx

• MessageBox is a perfectly horrid error handling mechanism. Instead, you should try to get error data to the people who can handle it. So: if you don’t think a problem is severe enough to crash, but would still like to get it, put instrumentation in to send it to yourself. (At Microsoft this is called “Generic Watson.” http://blogs.msdn.com/chris_pratley/archive/2004/02/04/67276.aspx)

This point really can’t be overstated. Having code to talk to yourself is how you catch and fix odd customer errors.

• You should understand completely how your components can fail, and should wrap the cases where there are complex failure conditions. Take the registry as an example: even when the function doesn’t fail with an error code, it can have really wierd postconditions.

  1. Wide char string with 21 bytes when it should be divided by 2
  2. Wide char string with more than one null-terminator
  3. Wide char string without any null terminator
  4. QWORD value with 16 bytes (documented to have 8 bytes – 64 bit number)
  5. Value of type REG_NONE
  6. Strings with zero size for which query is not setting the null terminator
  7. There are more, too.

• Test your error cases.