libcap: make -e causing trouble

oe-core 51540b64f62234c145fc32cfa3fbbaaebbeece08 altered libcap.inc (at the time) to append to EXTRA_OEMAKE rather than assign to it. The default value for EXTRA_OEMAKE contains "-e". This means that the change caused "-e" to be passed to make for the first time.

Unfortunately passing "-e" subtly changes the behaviour of libcap's Make.Rules under recursive make when prefix="" (which it is for us since we're using meta-micro.) Here's a snippet of Make.rules:

ifdef prefix
exec_prefix=$(prefix)
lib_prefix=$(exec_prefix)
inc_prefix=$(lib_prefix)
man_prefix=$(prefix)/share
else
prefix=/usr
exec_prefix=
lib_prefix=$(exec_prefix)
inc_prefix=$(prefix)
man_prefix=$(prefix)/share
endif

Without "-e" the prefix comes from the command line in both the parent and submakes. This takes precedence over any attempt to reassign it with a simple "=" operation so the headers are correctly installed in (empty string)/include.

With "-e" the prefix still comes from the command line in the parent make but from the environment in the submake. The attempt to assign it fails in the parent make as before, but not in the submake so the headers are installed incorrectly in /usr/include.

In all four cases the "ifdef prefix" else clause is executed.

The quick-and-easy fix for this is simply to pass prefix="${prefix}/" but it's really just working around the problem.

Alternatively we could go back to assigning EXTRA_OEMAKE rather than appending to it.

What would be the preferred course of action?

Quoted 3 lines · Mike Crowe

Unfortunately passing "-e" subtly changes the behaviour of libcap's Make.Rules under recursive make when prefix="" (which it is for us since we're using meta-micro.)

Given our use of make -e (with MAKEFLAGS= to try to prevent it from flowing into submakes) was always a hack to try to let things "just work", I think wherever possible we should stop relying on it, and explicitly pass everything the way that particular make-based buildsystem expects, personally. Better to be explicit than to rely on implicit "magic". Further, that behavior encourages recipe maintainers to not even read the buildsystem of the project they're creating a recipe for, which often leads to problems down the road..

Quoted 3 lines · Christopher Larson

Quoted 2 lines · Mike Crowe

Unfortunately passing "-e" subtly changes the behaviour of libcap's Make.Rules under recursive make when prefix="" (which it is for us

since

Quoted 1 line

Quoted 1 line

we're using meta-micro.)

[snip]

Quoted 1 line

Given our use of make -e (with MAKEFLAGS= to try to prevent it from

flowing

Quoted 1 line

into submakes) was always a hack to try to let things "just work", I

think

Quoted 5 lines

wherever possible we should stop relying on it, and explicitly pass everything the way that particular make-based buildsystem expects, personally. Better to be explicit than to rely on implicit "magic". Further, that behavior encourages recipe maintainers to not even read the buildsystem of the project they're creating a recipe for, which often

leads

Quoted 1 line

to problems down the road..

I completely agree, but what is the best way to avoid "-e". Is there ever likely to be anything else in EXTRA_OEMAKE that would need to be preserved?

I notice that autotools.bbclass just sets EXTRA_OEMAKE = "" so perhaps it's relatively safe to just assign it directly.