Re: using the date relationship of two older files as a prerequisite

[Brian J. Murrell]

On 12-12-07 10:53 AM, Mason wrote:
> 
> OK, so "O" is just like a normal source file; it is not created by make,
> and it is created/updated by your text editor.

Correct.  "O" is not created by make, but it's not created in real-time
either like an editor file is.  That is, it can get updated but even
when it does while it will be newer than it was before, it will still be
older than the target "T".

> This paragraph does not make sense (to me).
> 
> At some point, "O" is modified (possibly several times).

Correct.

> Suppose the "O" was last modified at T1.
> Then you call make, which builds "T" at T2.

Right.

> Obviously T1 < T2

Correct.

> If "O" is modified (possibly several times) at T3,
> then "O" is obviously newer than "T" since T2 < T3.

No.  O is modified at let's call it T1.5. (not T3).  It's newer than T1
but older than T2.

> What am I missing?

I think you were missing that O is modified at T1.5 after T was rebuilt
at T2.

The reason O can have a time of T1.5 after T2 is because O lives in an
external source that make can see.  That source can be updated but the
latency between it being updated and made available to make is so long
that the updated O is still some time in the past, before T2 in most cases.

b.

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