NetNews Usenet Archive 1993 #1/NN_1993_1.iso/spool/comp/sys/mac/programm/21216

Internet Message Format | 1993-01-11 | 3.2 KB

Path: sparky!uunet!gatech!destroyer!news.itd.umich.edu!potts
From: [e-mail] (Paul Potts)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Think C bug? [sprintf]
Date: 11 Jan 1993 22:14:32 GMT
Organization: Instructional Technology Laboratory, University of Michigan
Lines: 52
Message-ID: <[e-mail]>
References: <[e-mail]> <[e-mail]> <[e-mail]>
NNTP-Posting-Host: helen.oit.itd.umich.edu

In article <[e-mail]> [e-mail] (M. Scott Smith) writes:
>Hi..  I'm the original poster who asked about potential problems with sprintf.
>
>It sounds like some people have had no problems with sprintf, while others
>have.  I wasn't sure if it was commonly used by Mac C programmers; are there
>Toolbox calls (non-ANSI) that Mac pros tend to use instead?

It depends on what you want to do. Basically, sprintf gives you the
functionality of printf (formatted printing of strings, characters, etc.)
to memory instead of to a device. Like printf, sprintf is not type-safe;
it doesn't know about the types of things that you send it. The
routine will try its best to do what you tell it, but if you give it, for
example, a short quantity to print when you've told it via the formatting
information to expect a longword, the results will be, as they say,
"undefined."

I've used sprintf pretty extensively in XCMDs. I'll mention a few details
to the newsgroup; if you want help on why some specific piece of code doesn't
seem to work, I'd be happy to take a look at it by mail. One of the nice things
about sprintf is that it doesn't require the full ANSI library; you can
use ANSI-small or ANSI-A4 for code resources.

>
>Does sprintf only operate with arrays of characters, or will it be happy with
>types like Str255?  Or do I have to coerce Str255's to make them work?

Like most of the string-handling functions in C, sprintf uses the generic
type char * (pointer to character) as its argument, and this is what gets
written to. If you're using sprintf you must make sure that your destination
is what you expect it to be. If you're using the type Str255, remember that
sprintf will write strings in the zero-terminated format, whereas Pascal code
and a lot of the Toolbox functions expect strings in the length-first format.
THINK C has a quickie function which will do this conversion.

>think some of my problems were traced back to that.  At the same time, I wasn't
>sure what the problem was, because something would compile fine one way but
>not the next.  (It seems if Think C saw me passing a Str255 to sprintf it
>was happy about it; but if later in the program I passed a "real" string to
>it, then it suddenly saw problems with one of the calls..

Again, post an example...

>Is sprintf the best way to capture the functionality of Pascal's concat?

For this you might want to look into using the C function strcat, which
will append one string on to another. Keep in mind that C strings can be
any length, but if you expect to convert the string back to a Pascal-form
string you must be sure that it will fit.

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