Re: Pre-compiled headers

[Doug Landauer <landauer at apple dot com>]

At 10:36 AM -0800 2000/1/12, Per Bothner wrote:
> I vaguely remember that RMS's partially implemented design used
> a third idea:
> 
> #3 Only scan certain definitions if they are needed in the actual
> program.  I don't remember how this was done.

For what it's worth, this was implemented in the "cpp-precomp"
at NeXT, and worked (still works) pretty well for C.  It had to do
more actual parsing than a regular cpp, which is one reason why
Apple has not extended that to work with/for C++.  Steve Naroff
tells me that there was a paper published in the ACM somewhere,
that described this work.

> #2a:  Instead of just tokenizing each header file, we store
> a pre-compiled version that actually contains tree nodes
> in the binary format of the host system.
> [...] performing relocation.  Relocation means walking
> over the tree nodes and fixing up pointers.

Apple's "MrC"/"MrCpp" compiler for Mac OS  uses a scheme like this
one -- it seems to work pretty well in that context.

  -- Doug