Re: why doesn't this macro work!?

[Eric Blake]

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Please don't top-post on technical lists.

According to John Wohlbier on 3/8/2009 12:42 AM:
>> but other variations give me
>> -DDBC=\$withval
>> -DDBC=\$DBC
>>
>>                 AC_MSG_NOTICE([setting level of DBC to $withval])
>>                 AC_DEFINE(DBC, $withval)

> Of course I figured it out the minute after I sent the mail.
> AC_DEFINE_UNQUOTED.
> I can't claim to understand exactly why, but it works.

AC_DEFINE behaves as if it is part of a quoted shell here-doc (cat
<<\EOF), hence things such as $ are taken literally.  AC_DEFINE_UNQUOTED
behaves as if it is part of an unquoted shell her-doc (cat <<EOF), so
variable expansions can occur.  Thus, any time you want shell expansions,
you are correct that you have to use the alternate macro.

Meanwhile, you are missing recommended m4 quoting; the better way to write
this would be:

AC_DEFINE_UNQUOTED([DBC], [$withval])

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

Eric Blake             address@hidden
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