Re: regression in autoconf-2.62 vs. 2.61

[Eric Blake]

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According to Stepan Kasal on 6/5/2008 10:28 AM:
| Hello,

Hi Stepan, Ralf,

|
| I'd like to propose a solution, please speak up if you are not
| satisfied with it.  (If we reach an agreement, I'm willing to prepare
| a patch later.)

Well, now that Ralf has patched the code to strip comments after #undef
lines in the template file, we really ought to tighten the documentation.
~ Any volunteers?

|
| First, let me state that, strictly speaking, this is not a
| regression.  The Autoconf manual says that the #undef line cannot
| contain anything after the symbol.   And in that case, all versions
| tested by Ralf do the same.
|
|
| I suggest to add a note to the manual along these lines:
|
| ``
| Generally speaking, all #define and #undef directives in the header
| template may be modified by config.status, under some circumstances.
| Consequently, if you need to define or undefine a symbol under some
| circumstances (#ifdef THIS #define THAT, etc.), you should place
| those directives outside the config headers.  If you absolutely need
| to hook that to the config header itself, please put these directives
| to a separate file, and #include it from the config header template.
| (If you are using autoheader, you would probably use AH_TOP or
| AH_BOTTOM to inject the #include directive.
|
| For certain symbold it is important to avoid #undef ... [explanation
| about _POSIX_WHATEVER].
| To achive this, current Autoconf comments out _all_ remaining #undef
| directives remaining in the config header at the end of the
| instatiation, but this may change in future releases.
| ''
|
| WDYT?

Looks like a reasonable start, but be careful for typos (such as symbold).
~ I'll gladly review a texinfo-markup version, if I don't get around to
writing one first.

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

Eric Blake             address@hidden
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