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Mail Archives: djgpp/1997/06/28/17:32:06

Newsgroups: comp.os.msdos.djgpp
From: tob AT world DOT std DOT com
Subject: Re: Precompiled headers.
Message-ID: <EC5Epq.2Cz@world.std.com>
Sender: tob AT world DOT std DOT com (Tom Breton)
Reply-To: tob AT world DOT std DOT com
Organization: BREnterprises
References: <33AAD839 DOT 34ED AT cs DOT com>
Date: Sat, 21 Jun 1997 23:03:26 GMT
Lines: 34
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

"John M. Aldrich" <fighteer AT cs DOT com> writes:
> Gregary J Boyles wrote:
>
> What are they?

Pick an answer. Precompiled headers are...

  * "precompiled" "headers".

  * The main reason why people complain that gcc compares unfavorable in
    compile-speed to commercial compilers. gcc doesn't have them.

  * the result of compiling just headers, just *once*, dumping the
    end-result to disk, and fetching it back for a body file that
    includes that header.

  * The main reason why ANSI C++/X3J16 says that #include <filename>,
    unlike #include "filename", doesn't have to read a real file of that
    name.

  * hard to implement because they have to be in sync between the
    preprocessing stage and the symbol-lookup stage, have to react to
    changes in the underlying "real" header, may be dependent on the
    order in which files are included, and I strongly suspect that many
    things you *wouldn't* do in a normal header, such as ending halfway
    thru a declaration, you *couldn't* do in a precompiled one.


> And why would you want them?

Ask me that when I'm waiting for a long compile on a trivial change.

        Tom

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