unrecognized CFLAGS and CXXFLAGS

[romanchyla]

Hi, Thank you for putting the sample project together, I'd like to report a problem on Ubuntu 14.04 LTS

CFLAGS_STD        = -std=gnu11
CXXFLAGS_STD      = -std=gnu++11

are not recognized options, compilation failed.

/usr/bin/avr-gcc -MMD -c -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=100  -D__PROG_TYPES_COMPAT__ -I/usr/share/arduino/hardware/arduino//cores/arduino -I/usr/share/arduino/hardware/arduino//variants/standard    -Wall -ffunction-sections -fdata-sections -Os -std=gnu11 /usr/share/arduino/hardware/arduino//cores/arduino/WInterrupts.c -o /dvt/workspace/company/hw/arduino/bin/BarProject/uno/core/WInterrupts.o
cc1: error: unrecognized command line option "-std=gnu11"
make: *** [/dvt/workspace/company/hw/arduino/bin/BarProject/uno/core/WInterrupts.o] Error 1

I have updated my toolchain to gcc4.8 (and also g++, cpp) http://askubuntu.com/questions/271388/how-to-install-gcc-4-8

But the problem persists, do you think it is because of an old avr-gcc? Is there a way around it? (the build from source seems rather daunting)

avr-gcc -v
Using built-in specs.
COLLECT_GCC=avr-gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/avr/4.5.3/lto-wrapper
Target: avr
Configured with: ../src/configure -v --enable-languages=c,c++ --prefix=/usr/lib --infodir=/usr/share/info --mandir=/usr/share/man --bindir=/usr/bin --libexecdir=/usr/lib --libdir=/usr/lib --enable-shared --with-system-zlib --enable-long-long --enable-nls --without-included-gettext --disable-libssp --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=avr
Thread model: single
gcc version 4.5.3 (GCC) 

I have solved 'my problem' by editing the flags in the Makefile.

CFLAGS_STD        =
CXXFLAGS_STD      = -std=gnu++0x

It then compiles and uploads/works well. BUT I'm not sure what these flags do and if it is safe to ignore them - according to https://gcc.gnu.org/gcc-4.7/changes.html, the gnu++0x is equivalent of gnu++11 (so it should be safe), but I don't understand C and the gnu11.

Can you please shed some light on it?

[romanchyla]

this helped me fill the gap: https://github.com/WeAreLeka/Arduino-Makefile/blob/master/arduino-mk-vars.md#cxxflags_std

I think it might be useful adding warning directly into the Makefile, next to the CXXFLAGS.... something like:

Values depend on the installed versions of your gcc/c++/avr-gcc and the code that is being compiled For details, see: https://github.com/sudar/Arduino-Makefile/blob/master/arduino-mk-vars.md#cxxflags_std

[ladislas]

Hi @romanchyla,

Thanks for reporting this issue :+1: You're right, I will add a warning about the flags regarding the -std= option.

On Ubuntu, gcc and avr-gcc are independent. And your version avr-gcc 4.5.3 is rather old. To use avr-gcc 4.8.x you must run the following:

$ sudo apt-get update && sudo apt-get upgrade
$ sudo apt-get install gcc-avr binutils avr-libc avrdude

And you should have the following:

[romanchyla]

oups, you are right! i've started on ubuntu 11 and did the upgrade, but I haven't verified that i was on 14.04 (and I wasn't! silly old me...). i can confirm that it now works with the gnu11 options, well at least I learnt somehting extra about C standards :)