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Re: AC_C_BIGENDIAN answers "universal" on powerpc-aix

From: Eric Blake
Subject: Re: AC_C_BIGENDIAN answers "universal" on powerpc-aix
Date: Fri, 15 Aug 2008 21:53:32 -0600
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According to Peter O'Gorman on 8/15/2008 9:09 AM:
> Having a #define in an AH_VERBATIM/AH_TOP/AH_BOTTOM block gives
> undefined behavior? I'm not sure that there are many
> AH_VERBATIM/AH_TOP/AH_BOTTOM blocks without a #define, certainly very
> few that I have written :(

Hmm.  Gnulib has its fair share of AH_VERBATIM that use #define.  And your
argument for why #define is needed makes sense.

On rereading what was recently patched, the section on Header Templates
states "The use of `#define' instead of `#undef', or of comments on the
same line as `#undef', is strongly discouraged.";a=commitdiff;h=6d04538

Then it mentions autoheader as an alternative to maintaining
by hand.  And in the Autoheader Macros node, it states "Please note that
`text' gets included ``verbatim'' to the template file, not to the
resulting config header, so it can easily get mangled when the template is
processed." (although that statement is under AH_BOTTOM rather than
directly tied to AH_VERBATIM).  But it states nothing about whether
#define runs the risk of being mangled.

Sounds like we need a follow-up doc patch; anyone care to write a first
draft?  Ralf, you are more familiar with the current state of
config.status code than me; are we sure that only #undef patterns in the
template file are modified, and that #define is intended to make it
through AH_VERBATIM unmolested?  Is the testsuite sufficiently testing this?

At any rate, you've overcome my two (non-)nits by good argumentation, and
I think your patch is ready.  Please push, or let me know if I need to help.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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