Re: [Freeciv-Dev] patch: provide snprintf

[David Pfitzner <dwp@xxxxxxxxxxxxxx>]

Greg Wooledge wrote:

> If I'm reading this right, it allocates a region of memory and uses
> mprotect(2) to cause the program to get a SIGSEGV if it writes outside
> this version.  Then it writes chars to this region using the standard
> vsprintf(3).
> 
> Does this work on all Unix systems?  I would imagine that there may be
> a few without sigaction(2) or mprotect(2) (or both).

Yeah, I agree it looks pretty scary.  Other alternatives used by
other projects/libs to provide snprintf seem to be:

- Mostly full re-implementation of printf (at least format/argument
  parsing).  (Eg JitterBug does this.)  Ouch.

- Implement enough to calculate an upper bound on the output length,
  dynamically allocate that, vsprintf to it, then strncpy, then free
  the temporary memory.  (Eg glib does this for g_snprintf if there
  is no native snprintf.)

Maybe one of these would suit us better.

> I don't have a clue what this would do under Win32, OS/2, AmigaOS, etc.

The current Win32 version uses Cygwin, which I would guess 
already provides a vsnprintf (?), in which case the ugly 
Unix-specific stuff would not be used at all.  No idea about 
others.

-- David