In order to add compiler flags to your PlatformIO project, add the following line to your build config(s) in platformio.ini
:
build_flags = -std=gnu++17
You can also use multiple lines:
build_flags = -std=gnu++17 -ffast-math
Full platformio.ini
example:
[env:d1_mini] platform = espressif8266 board = d1_mini framework = arduino monitor_speed = 115200 build_flags = -std=gnu++17