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Re: AS_IF


From: Paul Eggert
Subject: Re: AS_IF
Date: Sun, 4 Oct 2020 18:50:21 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0

On 10/4/20 4:40 PM, Bruno Haible wrote:
AFAICS, this is relevant for code written directly into configure.ac. But
inside an AC_DEFUN it is irrelevant, because required macros are hoisted
before the body of the AC_DEFUN anyway.

I was playing it safe based on this NEWS item from Autoconf 2.69c:

   - Autoconf macros that use AC_REQUIRE internally, are not safe to
     use inside of hand-written shell control-flow constructs.  Use
     AS_IF, AS_CASE, AS_FOR, etc. instead.  (See the “Prerequisite
     Macros” section of the manual for further explanation.)

Since I didn't know whether the macros in question used AC_REQUIRE internally, I played it safe.

But now that you mention it, AS_IF isn't needed here and I installed the attached further patch. Also, to help prevent others from making a similar mistake, I plan to reword the Autoconf NEWS item to start with something like "Autoconf macros that use AC_REQUIRE are not safe to use in hand-written shell control-flow constructs that appear outside of macros defined by AC_DEFUN."

Attachment: 0001-c-stack-avoid-AS_IF.patch
Description: Text Data


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