On Wednesday 26 July 2006 12:49, Graeme Geldenhuys wrote:
> > MyVariable:=MyVariable; // this is a workaround in rare cases.
>
> Can anybody that knowns the internals of FPC confirm if this will
> create extra work/code for the compiler?
It does create an assignment. At least with the fpc2.0.2 version I just
checked:
Compiled with "-al" for source lines and "-O3":
|.Ll2:
| .stabn 68,0,10,.Ll2 - P$TEST_ASSIGN
|# [10] x := x;
| movl -4(%ebp),%eax
Without optimization it even generates:
| .stabn 68,0,10,.Ll2 - P$TEST_ASSIGN
|# [10] x := x;
| movl -4(%ebp),%eax
| movl %eax,-4(%ebp)
Depending on the view point and application it might be negligible. It's
probably not a good idea to do that inside a tight loop, but in most
other cases those couple of bytes won't hurt.
Although, well ... I wouldn't depend on that behaviour, because the
variable still *is* as uninitialized as before, because the right hand
side of the expression assigned to it is. So if someone cares to write
code for a more stricter data flow analysis, the warning may at some
time reappear.
So this is no clean way to do it I'd say.
What is needed is a way to tell the compiler: "Trust me. I know what I'm
doing."[1] ;)
Vinzent.
[1] "{$SLEDGE_HAMMER ON}"?
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