compiler rebuild invalidates precompiled header

[Geoff Keating]

> Date: Mon, 17 May 2004 11:33:03 -0700
> From: Mike Stump <mrs@apple.com>

> That said, maybe we could bury the mod time of the compiler binary into 
> the PCH file.  This avoids cksumming the .text segment or some other 
> change like that and is fairly sensitive to _any_ changes.  Maybe the 
> driver, since it stats the file anyway, could pass that mod time of the 
> stat into the compiler on the command line and the compiler could write 
> that out to the PCH file and validate upon reading.

I thought of that at the time.  The problem is that it's too
sensitive; modification times can change for many reasons (like NFS
time skew, or copying a file from one place to another).

-- 
- Geoffrey Keating <geoffk@geoffk.org>