configure: do look for sed

[ggouaillardet]

Refs. #10392

Signed-off-by: Gilles Gouaillardet [email protected]

[awlauria]

Interesting, I'm not sure how this ever worked.

[jsquyres]

This must be getting invoked implicitly somehow in at least some cases. With AC 2.71 on my Mac, I see this in configure output (before this PR is applied):

checking for a sed that does not truncate output... /usr/bin/sed

Maybe that doesn't always happen in all versions of Autoconf...? 🤷‍♂️

Regardless, it does not hurt to explicitly invoke this to ensure that $SED is set.

[jsquyres]

Answering my own question: I see what's happening. Yes, something is invoking this implicitly: $SED ultimately does get defined. But the error message that #10392 is referring to is apparently before $SED is defined (i.e., it's before the checking for a sed that does not truncate output... output that I cited). The error message occurs in some OMPI Fortran configury that probably doesn't have the same kind of machinery to ensure that $SED is defined. It's likely either an Autoconf bug or a bug in our Fortran configury.

Putting AC_PROG_SED at the top of configure.ac is a good solution.

[jsquyres]

That being said, putting the AC_PROG_SED where it is right now means that configure output looks like this:

checking for a sed that does not truncate output... /usr/bin/sed

============================================================================
== Configuring Open MPI
============================================================================

*** Prerequisites
checking for perl... perl
...etc

While that's certainly correct, it would be 17.2% nicer if that sed test output was below the Configuring Open MPI banner. 😄

[awlauria]

We could just move the opal_show_title "Configuring project_name_long" to be right before this line to get that 17.2%

[ggouaillardet]

Agreed, sed is now a prerequisite and will be searched just before perl

BTW, how did you end up with 17.2%? Is there a reference I missed?

[jsquyres]

BTW, how did you end up with 17.2%? Is there a reference I missed?

It was a complex set of calculations involving many mathematical disciplines, including linear algebra, calculus, hokus pokus, and imaginarium. Mostly the last one. Actually, entirely the last one. 😜

[awlauria]

Should this also go to v4.0.x and v4.1.x?

[jsquyres]

Should this also go to v4.0.x and v4.1.x?

I just checked: it does not appear to be necessary on v4.0.x or v4.1.x. 🎉

[awlauria]

Interesting - is sed not used on those branches?

[jsquyres]

I didn't track down why it isn't necessary. But I checked both branches, and the same erroneous output (indicating that $SED is not set) does not appear in the configure output. I did this testing on my laptop, where the same GNU Autotools were used to replicate the bad $SED-is-not-set behavior on main/v5.0.x.

Something must be different on the v4.x branches -- either the Fortran tests don't use $SED or some dependency ordering is different than sed is searched for earlier, ... etc.