593
Subj : Re: malloc()
To   : borland.public.cpp.borlandcpp
From : Bob Gonder
Date : Thu Jun 24 2004 01:15 pm

Jan Vernimmen wrote:

>                         if ( more characters then strlen(b) )
>                         {
>			   free(b)
>			   b=malloc()   //I must check malloc, -> b=null
>                         }
>                         copy stuff.str to b

>Do not forget the main discussion:
>I had:
>       txtBuf = (char *)malloc( strlen( szInput ) + 1 );   // with problems 
>now and then
>
>I made
>       txtBuf = (char *)malloc( strlen( szInput ) + 2 );   // no problems in 
>the last 6 month
>
>In the last case malloc() seems to work fine!
>To my opinion malloc is working but for unknow reasons in the first 
>construction it takes the wrong size.

I think the problem may have had to do with the way you determined if
the buffer was too small.
	Consider this chain of events:
	b = malloc(100);
	*b=0;
	if( strlen(b)/*0*/ < strlen(newstring)/*20*/ )
		b=malloc( strlen(newstring)+1)
	if(strlen(b)/*20*/ < strlen(newstring)/*5*/)
	if( strlen(b)/*5*/ < strlen(newstring)/*30*/)
		b=malloc( strlen(newstring)+1)
Just way too wasteful.
Instead, I might add an int.
	int	LenBuf = 100;
	b = calloc(LenBuf);
	if( LenBuf-1 < strlen(newstring)/*120*/ )
		/* Borland specific? mem manager optimize*/
		LenBuf = (((strlen(newstring)+1+4)+15)&~15)-4;
		b=malloc( LenBuf)

.

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