; https://docs.platformio.org/en/latest/projectconf/sections/env/options/build/build_flags.html
build_flags =
; The default for Apple Clang is… `c++98` o.O
; https://discord.com/channels/583251190591258624/1075788561334415360
;
; The default for ESP8266 toolchain is `gnu++17`:
; https://github.com/esp8266/Arduino/blob/master/platform.txt#L43
-std=gnu++20
; Enables many recommended warnings at once
; https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
-Wall
The NXP LPC platform with mbedos as the framework will use GCC 9.2.1 by default
this compiler should be capable of C++17 and C++2a per this.
Make sure that in the standard settings (without build_unflags and build_flags), it was actually using gnu++11. Otherwise your build_unflags = -std=gnu++11 is incorrect. Check project tasks → Advanced → Verbose Build and look for the compile command on a .cpp flie.
You can chose a different compiler, up to GCC 12.3.1, per available versions and documentation, as a change of the toolchain-gccarmnoneeabi pacakge.