Cannot compile C++11 code via Makefile

Question

I am building my Arduino project with a makefile:

BOARD_TAG = uno
ARDUINO_PORT = /dev/ttyACM0
USER_LIB_PATH = /home/prakhar/dev/alfred/arduino/libraries
CPPFLAGS=-x c++ -std=c++11 -Wall -DUNIX_ENVIRONMENT -DHAVE_NAMESPACES -DHAVE_STD
include /usr/share/arduino/Arduino.mk

I keep getting this error:

cc1plus: error: unrecognized command line option "-std=c++11"

I googled and this says that I need to update g++/gcc. I already have the newset versions:

prakhar@sim74stic ~ $ avr-g++ --version
avr-g++ (GCC) 4.9.1
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

prakhar@sim74stic ~ $ avr-gcc --version
avr-gcc (GCC) 4.9.1
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

prakhar@sim74stic ~ $ g++ --version
g++ (GCC) 4.9.1 20140903 (prerelease)
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

I installed arduino from the AUR (packages aur/arduino 1:1.0.6-1 and aur/arduino-mk 1.3.4-2). Can anybody point out what I'm doing wrong?

Answer 1

As I turns out, the avr-gcc (GCC) 4.9.1 goodies weren't being used at all! The arduino package was using a decrepit version of gcc,

prakhar@sim74stic ~ $ /usr/share/arduino/hardware/tools/avr/bin/avr-g++ --version
avr-g++ (GCC) 4.3.2
Copyright (C) 2008 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

prakhar@sim74stic ~ $ /usr/share/arduino/hardware/tools/avr/bin/avr-gcc --version
avr-gcc (GCC) 4.3.2
Copyright (C) 2008 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

All I had to do was specify:

AVR_TOOLS_DIR = /usr

to exexute with -std=c++11 flag (I also had to add an -fpermissive flag to compile C with g++).