• DeadlySins

The "Deadly Sins" from P. J. Brown's Writing Interactive Compilers and Interpreters Wiley 1979. We've committed them all at least once in GCC.

The deadly sins are:

1. to code before you think.
2. to assume the user has all the knowledge the compiler writer has.
3. to not write proper documentation.
4. to ignore language standards.
5. to treat error diagnosis as an afterthought.
6. to equate the unlikely with the impossible.
7. to make the encoding of the compiler dependent on its data formats.
8. to use numbers for objects that are not numbers.
9. to pretend you are catering to everyone at the same time.

10. to have no strategy for processing break-ins.
    

    • (A break-in is when you interrupt an interactive compiler, and then possibly continue it later. This is meaningful in an environment in which the compiler is run dynamically, such as many LISP and some BASIC environments. It is not meaningful for typical uses of C/C++ (although there was at least one interactive C environment according to Chris Lattner).)
11. to rate the beauty of mathematics above the usability of your compiler.
12. to let any error go undetected.
13. to leave users to find the errors in your compiler.