Earlier quoted context omitted.
Seems like the rules for C web development are the same as for any other language: don't trust user input, and delegate the sanitization to vetted library functions. It's not like it's 1991 and you have to use plain arrays and strcmp; there are really good, safe libraries for these things. That said, doing web development in a language with neither a REPL nor built-in unicode support sounds like a Bad Time.
Still an order of magnitude easier not to shoot yourself in the foot in most higher level language. Pretty sure you still have to use plain arrays and strcmp, what are these "safe" libraries you were going to use? Unless we are talking about C++ here? Also C supports unicode fine (to the extent it supports strings) and REPL can't hardly be considered a requirement for web development considering Java, .NET and PHP* d…
Also you should compile your app with apparmor and run it under grsecurity.
REPL like behaviour you can get with gdb. :)