Getting Arduino IDE to compile for C++14 - c++

Question

I've been looking to modify the build flags under Arduino's IDE 1.x, or even the Arduino CLI (which I haven't used but am willing to adopt) such that I can undefine -std=gnu++11 and instead define -std=gnu++14
I found a question related to this which gives me almost what I need:
Arduino 1.0.6: How to change compiler flag?
But it only shows how to add flags, not to remove them. I found another related post about changing arduino to GNU C++17 but the answer was it's not possible.
In this case, I know it's possible, as I do it in Platform IO in order to use the htcw_gfx library. It works great on most platforms that will run GFX reasonably anyway.
But I just don't know how to fiddle with Arduino to get it to dance the way I need to.
Any help would be greatly appreciated.

Answer 1

You can modify the default compile flags in the hardware/arduino/avr/platform.txt file.
$ grep -n "std" hardware/arduino/avr/platform.txt
23:compiler.c.flags=-c -g -Os {compiler.warning_flags} -std=gnu11 -ffunction-sections -fdata-sections -MMD -flto -fno-fat-lto-objects
28:compiler.cpp.flags=-c -g -Os {compiler.warning_flags} -std=gnu++11 -fpermissive -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -Wno-error=narrowing -MMD -flto
For some linux systems the following would work to automatically do this:
dirname $(realpath $(which arduino)) | xargs -I{} sed -i "s/\(std=gnu++1\)1/\14/" {}/hardware/arduino/avr/platform.txt
But this is not very portable, and will not work if the user has installed Arduino with Snap (as snap has these files mounted RO).
Sources:
https://stackoverflow.com/a/28047811/6946577
https://stackoverflow.com/a/55254754/6946577