[zedshaw]

> but no function with that signature could possibly work in this case.

This is the source of the bugs in C. People write functions that only work given all calls to them are never changed, which is absurd. Good modern C code involves trying to protect against bad usage and adding defensive checks.

So yes, the built-in strcpy is crap which is why most competent C doesn't use it except in a few rare cases where it's required.

And this does demonstrate actual bugs in the code. I wrote a test case that causes it, which incidentally is a common bug in C code called a buffer overflow. It's because of code examples like this that get copied to other situations that we have these defects.

[tptacek]

High level string libraries are a win.

But you may be overstating your case a bit.

From my codebase/third-party directory on my laptop (a bit random, I admit), from those projects I'd consider "competent C" (ie, not OpenSSL or MRI ruby):

* dovecot uses ASCIIZ strings and libc string functions

* redis uses ASCIIZ strings and libc string functions

* nginx uses a high-level buffered string library

* lcamtuf's skipfish scanner uses ASCIIZ strings and libc string functions

* libevent uses ASCIIZ strings and libc string functions

* qmail uses djb's string library

* memcached uses ASCIIZ strings and libc string functions

It's probably good to be comfortable with both approaches.

I don't know that you actually made this claim, but you seem to have given people here the impression that you believe functions that work with ASCIIZ strings should be bulletproofed to handle non-ASCIIZ inputs. I couldn't agree with that argument, especially as an argument about K&R's code being rusty.

People here are jumpy though (they're commenting, like me, mostly because they're bored).

Looking forward to more examples from the book.

[aaronblohowiak]

Redis strings are actually length prefixed null terminated strings

[tptacek]

The string data type in the db? Because Redis itself uses char-stars all over the place, with the libc string functions.

[aaronblohowiak]

Hmm, reading the source it looks like he is using His sds string library, which has Len, size and a asciiz char* member. When last I checked he does pass the char* around (because it is null terminated) but he also sometimes will do pointer math to get back to the sds

[tptacek]

You're right; I was reacting to the count of char\s+star and snprintf calls, but only fair to chalk Redis up among the packages I have that rely on a high-level string library.

[gonzo]

this from the man who won't describe xargs to newbies because he doesn't understand it.

blargh