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From: Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups: comp.lang.c
Subject: Re: Allocate variables within code blocks.
Date: Sun, 08 Apr 2018 12:29:44 +0100
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"itsme.susila" <itsme.susila@gmx.com> writes:

> Allocate variables within code blocks
>
> Within a function, I will have many for loops:

I'd reconsider that design if I were you.  I suppose it depends on what
the program is, but short single-purpose function generally make for
better code.

> [code]
> void myfn(){
>  int, x, y, z;
> for (i = 0,...){
>    u64 u, v, w;
>
>    u = 3;
>    x = u * 6;
>    ......
>
>
> }
>
>
> return;
> }
> [/code]
>
> Which is the better practice (giving faster codes):
> Should I allocate u,v,w at the start of myfn(); I know beforehand they
> would be used many times over.

Modern compilers will generate good code in both cases.  It's almost
always better to write for clarity rather than generated code.  Once you
have a clear program, measure the performance to see what parts are
taking up the time.

-- 
Ben.