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From: ar4@sage.cc.purdue.edu (Piper Keairnes)
Newsgroups: comp.sys.mac.programmer
Subject: Re: ThinkC prototypes and Str255 args
Message-ID: <4449@sage.cc.purdue.edu>
Date: 15 Sep 90 20:35:32 GMT
References: <1990Sep15.154434.17307@midway.uchicago.edu>
Organization: Purdue University
Lines: 38

fri0@quads.uchicago.edu (Christian E. Fritze) writes:
>I'd like to be able to call functions which expect arguments of the type Str255
>with a string I build on the fly. If I try to pass a string to a function like
>SomeFunction("\pHere's my string");

There is one problem... C passes arguments by value. So, when you make a
call to some procedure that expects a Str255, it is expecting the entire
string array. When you make a call such as the one above, C is simply
passing a pointer to that string.

The workaround: Make and use a procedure like the one below...
Call like you want to... SomeFunction2("\pHere's my string");

SomeFunction2(s)
	char *s;
{
	int i;
	Str255 theString;        /* you may want to have some error detection */

	theString[0] = s[0];              /* copy length byte    */
	for (i=1; i<=theString[0]; i++)   /* copy rest of string */
		theString[i] = s[i];

	SomeFunction(theString);
}

All that this function does is takes your string literal and stores it in a
variable of type Str255 then calls the intended function with that variable.
You can do this yourself in your code, or make a small function like
above to handle the interface and keep you code a little cleaner. This is
what we get for programming in C on a machine that was written in Pascal!

Please don't flame my code, I wrote it on the fly while reading news.

-----
Piper Keairnes - Computer Science   ** Purdue University Computing Center **
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