5 ms·

Good for laughs. Thanks. Now the serious follow up: Ok, what else should someone do? Programs (often) handle text. Apparently, that pretty much means you're fu

Good for laughs. Thanks. Now the serious follow up: Ok, what else should someone do? Programs (often) handle text. Apparently, that pretty much means you're fucked. So what is a reasonable way to write such programs?

dllthomas 13y ago
If you're able, don't treat text as zero-terminated char arrays. Ideally, you'd have a well fleshed-out library for encoding-aware ropes.
- Arnor 13y ago
  Which libraries do you recommend?
  - dllthomas 13y ago
    Unfortunately, I don't know of one. My recent C work has worked with text only in a very limited capacity (parsing and building packets in an ascii format - for the later, vectorized write buffers are a poor-man's ropes). Edited to add: Apparently there is this: http://www.hpl.hp.com/personal/Hans_Boehm/gc/gc_source/cordh.txt http://www.hpl.hp.com/personal/Hans_Boehm/gc/gc_source/cordh...
  - oofabz 13y ago
    I recommend bstring for length-prefixed strings in C: http://bstring.sourceforge.net/ http://bstring.sourceforge.net/
    - clarry 13y ago
      Bstring relies on undefined behavior for security. Don't use it if you care about security.
cube13 13y ago
Make damned sure you know what you're doing. That means making sure you have enough memory allocated to avoid overflows, and that any input is sanitized before putting it down. Meaning, if you're using a function that's expecting a null terminated string, make SURE it's null terminated before copying. Or that you know the exact length to pass into a length specified function. The problem isn't necessarily the functions themselves, it's coders who make assumptions that don't pan out to be true.
thinkpad20 13y ago
Do all of your string work with these guys: struct string { char *str; unsigned length; }
- _telemachus 13y ago
  Let's assume your string struct is solid. Then does that mean you can safely use it with `printf, fprintf, sprintf` (e.g. printf("%s", string->value)? Or must you also write custom versions of those functions? How deep does this rabbit hole go?
  - thinkpad20 13y ago
    You don't have to write custom versions of any of those functions; just use the char pointer in the struct instead of a bare char pointer. Keeping track of the length of your strings gives an easy way to provide the 'n' in all of those 'n' functions, and has other advantages besides. But the use of such a struct in and of itself, of course, provides no guarantees of safety. There is no such thing in C anyway :)
  - dllthomas 13y ago
    You'd probably want "%.*s" or possibly even "%*.*s" if you want it space padded. In principle you can bound your space usage and avoid an snprintf with such constructs; in practice, it's probably better to still use snprintf (if you're using standard-library string functions at all).

dllthomas 13y ago

If you're able, don't treat text as zero-terminated char arrays. Ideally, you'd have a well fleshed-out library for encoding-aware ropes.

Arnor 13y ago
Which libraries do you recommend?
- dllthomas 13y ago
  Unfortunately, I don't know of one. My recent C work has worked with text only in a very limited capacity (parsing and building packets in an ascii format - for the later, vectorized write buffers are a poor-man's ropes). Edited to add: Apparently there is this: http://www.hpl.hp.com/personal/Hans_Boehm/gc/gc_source/cordh.txt http://www.hpl.hp.com/personal/Hans_Boehm/gc/gc_source/cordh...
- oofabz 13y ago
  I recommend bstring for length-prefixed strings in C: http://bstring.sourceforge.net/ http://bstring.sourceforge.net/
  - clarry 13y ago
    Bstring relies on undefined behavior for security. Don't use it if you care about security.

cube13 13y ago

Make damned sure you know what you're doing. That means making sure you have enough memory allocated to avoid overflows, and that any input is sanitized before putting it down. Meaning, if you're using a function that's expecting a null terminated string, make SURE it's null terminated before copying. Or that you know the exact length to pass into a length specified function. The problem isn't necessarily the functions themselves, it's coders who make assumptions that don't pan out to be true.

thinkpad20 13y ago

Do all of your string work with these guys: struct string { char *str; unsigned length; }

_telemachus 13y ago
Let's assume your string struct is solid. Then does that mean you can safely use it with `printf, fprintf, sprintf` (e.g. printf("%s", string->value)? Or must you also write custom versions of those functions? How deep does this rabbit hole go?
- thinkpad20 13y ago
  You don't have to write custom versions of any of those functions; just use the char pointer in the struct instead of a bare char pointer. Keeping track of the length of your strings gives an easy way to provide the 'n' in all of those 'n' functions, and has other advantages besides. But the use of such a struct in and of itself, of course, provides no guarantees of safety. There is no such thing in C anyway :)
- dllthomas 13y ago
  You'd probably want "%.*s" or possibly even "%*.*s" if you want it space padded. In principle you can bound your space usage and avoid an snprintf with such constructs; in practice, it's probably better to still use snprintf (if you're using standard-library string functions at all).