Review findings

My change is at D21295

Something like this is probably needed instead

~/git/freebsd2/lib/libsysdecode # git diff
diff --git lib/libsysdecode/Makefile lib/libsysdecode/Makefile
index 2be244a6da46..9edfe067063c 100644
--- lib/libsysdecode/Makefile
+++ lib/libsysdecode/Makefile
@@ -127,7 +127,8 @@ incdir=${SYSROOT:U${DESTDIR}}${INCLUDEDIR}
 tables.h: mktables ${incdir}/netinet/in.h ${incdir}/netinet/tcp.h \
     ${incdir}/netinet6/in6.h
        sh ${.CURDIR}/mktables ${incdir} ${.TARGET}.tmp && \
-           mv -f ${.TARGET}.tmp ${.TARGET}
+           mv -f ${.TARGET}.tmp ${.TARGET} && \
+           mv -f .depend.${.TARGET}.tmp .depend.${.TARGET}

The hacks to using tables.h.tmp is probably what broke my work.

This already has .depend file support. Why is this needed?

Which package provides clang? I don't have a /usr/local/bin/clang on my system.

This doesn't seem to fix the SIGKILL issue.

~ # procstat -kk 19680
  PID    TID COMM                TDNAME              KSTACK
19680 101200 python2.7           -                   __mtx_lock_sleep+0x118 __mtx_lock_flags+0x102 _sleep+0x334 umtxq_busy+0xb7 do_sem_wait+0x150 __umtx_op_sem_wait+0x6e amd64_syscall+0x2bb fast_syscall_common+0x101
19680 101634 python2.7           -                   mi_switch+0x174 sleepq_switch+0x110 sleepq_catch_signals+0x417 sleepq_wait_sig+0xf _sleep+0x2d0 umtxq_sleep+0x153 do_sem_wait+0x41c __umtx_op_sem_wait+0x6e amd64_syscall+0x2bb fast_syscall_common+0x101
19680 101635 python2.7           -                   _mtx_lock_spin_cookie+0x231 __mtx_lock_spin_flags+0xf8 wakeup_one+0xf do_sem_wait+0x26f __umtx_op_sem_wait+0x6e amd64_syscall+0x2bb fast_syscall_common+0x101
~ # kill -9 19680
~ # procstat -kk 19680
  PID    TID COMM                TDNAME              KSTACK
19680 101200 python2.7           -                   __mtx_lock_flags+0xc1 do_sem_wait+0x218 __umtx_op_sem_wait+0x6e amd64_syscall+0x2bb fast_syscall_common+0x101
19680 101634 python2.7           -                   mi_switch+0x174 sleepq_switch+0x110 sleepq_catch_signals+0x417 sleepq_wait_sig+0xf _sleep+0x2d0 umtxq_sleep+0x153 do_sem_wait+0x41c __umtx_op_sem_wait+0x6e amd64_syscall+0x2bb fast_syscall_common+0x101
19680 101635 python2.7           -                   __mtx_lock_sleep+0x118 __mtx_lock_flags+0x102 do_sem_wait+0x148 __umtx_op_sem_wait+0x6e amd64_syscall+0x2bb fast_syscall_common+0x101
~ # procstat -i 19680|grep -v -- ---|grep KILL
19680 python2.7        KILL     P--

This is a massive POLA violation. What the hell. You took a flag that was intended to make <some effort> to overwrite data and made it SILENTLY DO NOTHING. That's insane.

Ports approved

Technically seems fine.
Feels like a POLA issue though. If I happened to have some package installed then buildworld behaved differently.
Maybe CROSS_TOOLCHAIN=yes or CROSS_TOOLCHAIN=base?
I don't really care either way; default on like you have is fine too as I don't fully understand the use case.

Check out rP154065.
All of the PRs linked there were filed in GNATS but were mapped over in BUGZILLA so they had the same numbers.
Had they been GNATS urls they would be more annoying to deal with IMO as the links would all be dead now. I realize this is an objective opinion. I would be comfortable with simply "https://bugs.freebsd.org/12344" as that can likely work forever.

Jilles mentioned on IRC a simpler way in the wrapper to enable it without the set -o call:

command set -o pipefail 2>/dev/null || :

In D16868#415222, @bdrewery wrote:

In D16868#415167, @bdrewery wrote:

In D16868#415150, @bdrewery wrote:

Has this turned up any bad pipelines in Makefiles?

Ah right there is that dd one from a while back.
Now that pipefail is in we could do this a lot simpler like tools/install.sh works.
I don't think it needs to be a MK_ option.
It doesn't need to install.
Maybe something like this could work in tools/sh.sh that we just set with __MAKE_SHELL=?

#! /bin/sh
set -o pipefail 2>/dev/null || :
exec "$@"

Hmm set -o pipefail || : doesn't actually ignore the error.

# sh -ec 'set -o pipefail || :; echo test'
set: Illegal option -o pipefail

:(

In D16868#415167, @bdrewery wrote:

In D16868#415150, @bdrewery wrote:

Has this turned up any bad pipelines in Makefiles?

Ah right there is that dd one from a while back.
Now that pipefail is in we could do this a lot simpler like tools/install.sh works.
I don't think it needs to be a MK_ option.
It doesn't need to install.
Maybe something like this could work in tools/sh.sh that we just set with __MAKE_SHELL=?

#! /bin/sh
set -o pipefail 2>/dev/null || :
exec "$@"

In D16868#415150, @bdrewery wrote:

Has this turned up any bad pipelines in Makefiles?

Has this turned up any bad pipelines in Makefiles?

This seems incomplete. It's just fixing the specific cases having problems today?
Why shouldn't we mandate enabling case-sensitivity on the filesystem first?