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AC_CONFIG_HEADERS regression (was: Re: autoconf 2.61: AC_DEFINE variable

From: Stepan Kasal
Subject: AC_CONFIG_HEADERS regression (was: Re: autoconf 2.61: AC_DEFINE variable with parenthesis)
Date: Fri, 15 Dec 2006 16:21:21 +0100
User-agent: Mutt/

[ This is part 2 of 2 of my answer to the report. ]


On Thu, Dec 14, 2006 at 02:32:54PM +0200, Andrey Simonenko reported
the following regression:

The temmplate:
> config.h.in:
> # define ABC
> # define DEF(x)

results in:
> [...] autoconf-2.59:
> /* config.h.  Generated by configure.  */
> # define ABC
> # define DEF(x)

> [...] autoconf-2.61:
> /* config.h.  Generated from config.h.in by configure.  */
> # define ABC
> # define DEF(x) somevalue

Further analysis:

I tested the following lines:
(The $ sign marks the end-of-line.)
1) #define ABC$
2) #define ABC $
3) #define ABC foo$
4) #define DEF(x)$
5) #define DEF(x) $
6) #define DEF(x) foo$

This matrix shows which of the template lines are recognized:
    2.59   2.61a
1)     n       n
2)     n       y
3)     y       y
4)     n       y
5)     n       y
6)     n       y

(And I have verified that the situation is the same if the #define is
replaced by "# define".)

So we observe a regression for templates 2), 4), 5), 6).
I'm afraid that it was my changes to status.m4 which introduced the
regression.  Perhaps I intended the case 6) and a ``fix.''

But on a second thought, I think all these regressions are unwanted:
Only the 3) is needed to support historical templates, the rest is just
undefined behaviour.  But since there seem to be no real reason to
regress from 2.59, we should try to keep the historical behaviour,
at least if it is easy to implement.

What do you think?

If there is a consensus that the regression should be fixed, I'll
try to write a patch.

Have a nice day,
        Stepan Kasal

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