From 697e56459c4d74cd4987e1273f18e47a912b4933 Mon Sep 17 00:00:00 2001
From: zrj <rimvydas.jasinskas@gmail.com>
Date: Wed, 12 Oct 2016 17:04:52 +0300
Subject: [PATCH] LTO: Prevent -flto being used in main system libraries.

There are subtle ways it can get broken specially in libc and libm.
(-plugin-opt=-pass-through=-lc)
Both libpthread.a and rtld-elf could have use of LTO but it is safer
for now not to expose internals. (affects only static libs)
---
 lib/libc/Makefile.inc     | 6 ++++++
 lib/libm/Makefile         | 6 ++++++
 lib/libthread_xu/Makefile | 7 +++++++
 libexec/rtld-elf/Makefile | 6 ++++++
 4 files changed, 25 insertions(+)

diff --git a/lib/libc/Makefile.inc b/lib/libc/Makefile.inc
index 1f0be47152..5c2c9fe1e8 100644
--- a/lib/libc/Makefile.inc
+++ b/lib/libc/Makefile.inc
@@ -12,6 +12,12 @@ NOASM=
 
 WARNS=2
 
+# for now do not let the use of -flto (check -plugin-opt=-pass-through=-lc !)
+.if ${CFLAGS:M-flto}
+CFLAGS+=	-fno-lto
+LDFLAGS+=	-flto
+.endif
+
 .include "${.CURDIR}/../libc/${MACHINE_ARCH}/Makefile.inc"
 
 .include "${.CURDIR}/../libc/citrus/Makefile.inc"
diff --git a/lib/libm/Makefile b/lib/libm/Makefile
index 616543ae15..d4dde120d0 100644
--- a/lib/libm/Makefile
+++ b/lib/libm/Makefile
@@ -114,6 +114,12 @@ PAST_SRCS = imprecise.c frexp.c isfinite.c isnanf.c isnormal.c signbit.c
 SRCS=	${COMMON_SRCS} ${PURE_SRCS}
 SRCS+=	${PAST_SRCS}
 
+# for now do not let the use of -flto
+.if ${CFLAGS:M-flto}
+CFLAGS+=	-fno-lto
+LDFLAGS+=	-flto
+.endif
+
 .if (${MACHINE_ARCH} == "x86_64")
 .PATH:		${OPENSRC}/src/ld80
 .PATH:		${.CURDIR}/src/amd64
diff --git a/lib/libthread_xu/Makefile b/lib/libthread_xu/Makefile
index ee4aa1563a..da4020aca0 100644
--- a/lib/libthread_xu/Makefile
+++ b/lib/libthread_xu/Makefile
@@ -2,6 +2,13 @@
 
 LIB=thread_xu
 SHLIB_MAJOR= 2
+
+# for now do not let the use of -flto
+.if ${CFLAGS:M-flto}
+CFLAGS+=	-fno-lto
+LDFLAGS+=	-flto
+.endif
+
 CFLAGS+=-DPTHREAD_KERNEL -D_THREAD_SAFE
 CFLAGS+=-I${.CURDIR}/../libc/include -I${.CURDIR}/thread \
 	-I${.CURDIR}/../../include
diff --git a/libexec/rtld-elf/Makefile b/libexec/rtld-elf/Makefile
index b06b039476..6a68dae827 100644
--- a/libexec/rtld-elf/Makefile
+++ b/libexec/rtld-elf/Makefile
@@ -13,6 +13,12 @@ WARNS?=		2
 # To activate LD_DEBUG functionality, define ENABLE_DEBUG
 # e.g. make -DENABLE_DEBUG
 
+# for now do not let the use of -flto
+.if ${CFLAGS:M-flto}
+CFLAGS+=	-fno-lto
+LDFLAGS+=	-flto
+.endif
+
 CFLAGS+=	-DIN_RTLD
 CFLAGS+=	-I${.CURDIR}/${MACHINE_ARCH} -I${.CURDIR} -D__thread=
 CFLAGS+=	-I${.CURDIR}/../../lib/csu/common
-- 
2.41.0