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From:	Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: new gcc 4.10 behaviour
Date:	29 Mar 2006 12:34:54 GMT
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Martin Steuer <martin AT x DOT invalid> wrote:

> And if not, why? Would the optimizer have to assume that the first call 
> to clock has changed the internal state of that function?

Generally it would --- but not if the two calles are initializers of
variables.

> And in general: how can one guarantee a certain order of execution for 
> code like that from the OP? 

By making them statements, rather than series of variable definitions.
That changes introduces what the C standard calls "sequence points",
which the optimizer must respect, and thus maintains order of things.

This would appear to be a side effect of the C99 feature allowing
variable definitions to occur in the middle of a block, rather than at
the start of it only.

-- 
Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.

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