Re: Call for port reports

Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > One other idea would be to set CFLAGS to "" before including template,
> > and just test to see if it is still "" after --- that might be cleaner
> > than saving the original value and comparing.
>
> Yeah, that bothered me a bit too --- what if the template tries to set
> CFLAGS to its already-existing value? I was thinking that unsetting
> CFLAGS before running the template would be the best answer.

I assume he did it that way so if you do:

CFLAGS=

in the template file that it would be honored. I see lots of this in
configure:

ac_env_CFLAGS_set=${CFLAGS+set}

but that uses 'set' if the variable is null or unset:

${parameter:+word}
Use Alternate Value. If parameter is null or
unset, nothing is substituted, otherwise the expan-
sion of word is substituted.

However, I thought null meant "", but I now think null basically means
the same as unset in this manual page. Notice that '+' tests only for
unset, and knows when you have done VAR= and VAR="":

$ echo ${Y+no}

$ Y=
$ echo ${Y+no}
no
$ Y=""
$ echo ${Y+no}
no
$ unset Y
$ echo ${Y+no}

$

so the proper test would be to unset the variable, then use ${var+val}
to test CFLAGS after the template file is included.

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