Re: [PATCH] don't let environment settings perturb build

[Jim Meyering]

Ralf Wildenhues wrote:
> * Jim Meyering wrote on Thu, Oct 15, 2009 at 09:06:16PM CEST:
>> Subject: [PATCH] don't let environment settings perturb build
>>
>> Setting the envvars, LIB_CLOCK_GETTIME, LIB_EACCESS or LIB_NANOSLEEP
>> could cause a configure-time and/or build-time malfunction.
>> Typically, a configure-time function-in-library test is performed
>> via code like this:
>>
>>   LIB_VAR=
>>   AC_SUBST([LIB_VAR])
>>   prefix_saved_LIBS=$LIBS
>>     AC_SEARCH_LIBS([FUNC], [LIB_NAME],
>>             [test "$ac_cv_search_FUNC" = "none required" ||
>>              LIB_VAR=$ac_cv_search_FUNC])
>>   LIBS=$prefix_saved_LIBS
>>
>> However, in each of the files affected by this change, the LIB_VAR=
>> initialization was omitted.  Thus, when set in the environment, its
>> value would propagate into generated Makefiles when FUNC is not found
>> in LIB_NAME.

Hi Ralf,

> Wouldn't it be just as consistent to just document that LIB_<VAR> can be
> used to override the respective macro, for systems on which a library
> other than one known to the macro, may be needed?

Most of the uses I saw already had the initialization.
I fixed the few that did not.  Add the fact that I've never
needed (or heard of a need) to pre-seed to override AC_SEARCH_LIBS
results, and that was enough for me.

> That would be in line with how many Autoconf macros work: the AC_SUBSTed
> variable may be overridden by the knowledgeable end user, who may know
> better than the macro author.
>
> Aside, have you experienced a configure-time and/or build-time
> malfunction with this?
>
>> * m4/clock_time.m4 (gl_CLOCK_TIME): Initialize AC_SUBST'd var.
>> * m4/euidaccess.m4 (gl_PREREQ_EUIDACCESS): Likewise.
>> * m4/nanosleep.m4 (gl_FUNC_NANOSLEEP): Likewise.

No.  However, I prefer to insulate code and tests from the
vagaries of the environment whenever possible/reasonable.