Daniel Stenberg <[EMAIL PROTECTED]> writes:
> On 18 Jun 2001, Hrvoje Niksic wrote:
>
>> There are good reasons to use alloca instead of malloc
>
> I know this is taken out of context, but I'm curious on this. What
> are the good technical reasons to use alloca instead of malloc?
* Reduced memory fragmentation -- you don't need to worry about
thousands of small mallocs fragmenting your heap, alloca always
allocates and flawlessly frees stuff off the stack.
* Easier coding -- you don't need to worry about freeing the value
before you return from the function.
* Faster resulting code -- alloca generates the code that simply moves
the stack pointer. malloc on the other hand is a genuine function
call which needs to search the heap for a "good match", resize the
heap if necessary, handle freeing, and be all around as fast as a
rabbit and as memory-efficient as the proverbial Scott with his
money, all at the same time. Obviously, one of these has to suffer.
> Aren't those occurences just giving you headache when porting wget
> to platforms that don't offer alloca()?
First, this problem has *never* occurred so far, and Wget has been
compiled on some very weird platforms. Second, the standard file
`alloca.c' distributed with Wget serves for exactly that purpose.
BTW, are you aware that popular (and portable!) GNU programs such as
GNU Emacs use alloca all over? If there were non-obvious significant
problems with hit, they would have been discovered by now.
So far, the amount of headache has been 0, whereas the benefits have
been significant.
