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Re: Having Trouble with m4 Input (m4 version 1.4.13)

From: Tom Browder
Subject: Re: Having Trouble with m4 Input (m4 version 1.4.13)
Date: Wed, 8 Sep 2010 06:15:04 -0500

On Tue, Sep 7, 2010 at 12:13, Gary V. Vaughan <address@hidden> wrote:
> On 7 Sep 2010, at 23:49, Tom Browder wrote:
>> On Tue, Sep 7, 2010 at 11:16, Tom Browder <address@hidden> wrote:
>> Well, duh, I just found "#pragma once" in GNU cpp--the answer for that
>> problem.  I vaguely remember reading about it once but...
> Though I haven't checked the docs or the code, I have a pretty strong 
> conviction
> that gcc is actually pretty smart without the pragma too... it remembers any
> headers that are entirely contained in cpp guards (inside the header file),
> and if it encounter another #include of the same file without a state change
> in the guard macro, it ignores the #include and gets on with the rest of the
> file.

Gary, you're correct.  Ian, one of the gcc developers, told the
gcc-help list, in response to my query. that "#pragma once" is
obsolete.  A cpp optimization takes care of it auto-magically, so I
don't need m4 for that.



Thomas M. Browder, Jr.
Niceville, Florida

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