From c4f0860660631b24cece97bfe8ec2bea5b56f038 Mon Sep 17 00:00:00 2001
From: Tim Niemueller <tim@niemueller.de>
Date: Mon, 6 Mar 2017 17:02:44 +0100
Subject: [PATCH] Arduino.mk: make LTO optional, enabled by default

On Fedora 25 with avr-gcc 6.2.0 LTO crashes, e.g., if Serial is used.
---
 Arduino.mk | 19 +++++++++++++++----
 HISTORY.md |  1 +
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/Arduino.mk b/Arduino.mk
index 82b4964..89e8149 100644
--- a/Arduino.mk
+++ b/Arduino.mk
@@ -1039,9 +1039,17 @@ ifndef AR_NAME
     endif
 endif
 
+ifeq ($(shell expr $(CC_VERNUM) '>' 490), 1)
+    USE_LTO ?= 1
+endif
+
+
 ifndef CFLAGS_STD
     ifeq ($(shell expr $(CC_VERNUM) '>' 490), 1)
-        CFLAGS_STD      = -std=gnu11 -flto -fno-fat-lto-objects
+        CFLAGS_STD      = -std=gnu11
+        ifeq ($(USE_LTO),1)
+            CFLAGS_STD += -flto -fno-fat-lto-objects
+        endif
     else
         CFLAGS_STD        =
     endif
@@ -1052,7 +1060,10 @@ endif
 
 ifndef CXXFLAGS_STD
     ifeq ($(shell expr $(CC_VERNUM) '>' 490), 1)
-        CXXFLAGS_STD      = -std=gnu++11 -fno-threadsafe-statics -flto
+        CXXFLAGS_STD      = -std=gnu++11 -fno-threadsafe-statics
+        ifeq ($(USE_LTO),1)
+            CXXFLAGS_STD += -flto
+        endif
     else
         CXXFLAGS_STD      =
     endif
@@ -1064,11 +1075,11 @@ endif
 CFLAGS        += $(CFLAGS_STD)
 CXXFLAGS      += -fpermissive -fno-exceptions $(CXXFLAGS_STD)
 ASFLAGS       += -x assembler-with-cpp
-ifeq ($(shell expr $(CC_VERNUM) '>' 490), 1)
+ifeq ($(USE_LTO), 1)
     ASFLAGS += -flto
 endif
 LDFLAGS       += -$(MCU_FLAG_NAME)=$(MCU) -Wl,--gc-sections -O$(OPTIMIZATION_LEVEL)
-ifeq ($(shell expr $(CC_VERNUM) '>' 490), 1)
+ifeq ($(USE_LTO), 1)
     LDFLAGS += -flto -fuse-linker-plugin
 endif
 SIZEFLAGS     ?= --mcu=$(MCU) -C
diff --git a/HISTORY.md b/HISTORY.md
index c772c04..2e1ebfe 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -7,6 +7,7 @@ I tried to give credit whenever possible. If I have missed anyone, kindly add it
 ### In Development
 - Fix: Do not include the Arduino header when calling generate_assembly on .cpp files. (https://github.com/Batchyx)
 - Fix: Auto-detect F_CPU on Teensy from boards.txt (https://github.com/DaWelter)
+- Tweak: Allow to disable LTO (currently crashes on Fedora 25)
 
 ### 1.5.2 (2017-01-11)