Confusing order in which the platformio.ini build_flags are passed to respective toolchains?

[Hermiedapwdrman]

Hello,

I am having an issue with the build flags when trying to configure the USB descriptors for the Teensy 3.1 board. Specifically I want to access the HID Keyboard/Mouse/Joystick functionality included in the Teensy libraries. These are contained within a preprocessor #if/#elif/#elif block determined by which value is defined during the compiler invocation. E.g.

#if defined(USB_SERIAL)
    <Setupo as CDC serial device>
#elif defined(USB_HID)
    <Setup as HID keyboard/mouse/joystick>
#endif

For the Teensy framework, you have defined USB_SERIAL within the teensy base platform and this is passed to the compiler during the run command. As per the platformio instructions to use build_flags rather than create new platforms, I tried using the following platformio.ini setup.

[env:teensy31]
platform = teensy 
framework = arduino
board = teensy31
build_flags =  -UUSB_SERIAL -DUSB_HID  

With the intent to un-define the included USB_SERIAL value and define USB_HID to enable that portion of the USB code. The problem I have encountered is the order which the build_flags are passed to the compiler. The above configuration fails to compile (due to undeclared functions which are declared within the USB_HID conditional code block). The console output after platformio run is:

arm-none-eabi-g++ -o .pioenvs/teensy31/src/mymain.o -c -fno-rtti -fno-exceptions -std=gnu++0x -felide-constructors -UUSB_SERIAL -g -Os -ffunction-sections -fdata-sections -Wall -mthumb -mcpu=cortex-m4 -nostdlib -MMD -DF_CPU=72000000L -DUSB_SERIAL -DLAYOUT_US_ENGLISH -D__MK20DX256__ -DUSB_HID -DARDUINO=10600 -DTEENSYDUINO=121 -DPLATFORMIO=010400 -I.pioenvs/teensy31/FrameworkArduino .pioenvs/teensy31/src/mymain.cpp

The '-UUSB_SERAL' option I declared is passed before the platform inherent '-DUSB_SERIAL' option, and as such does not clear it. I have not found a way to alter this order and this is preventing me from clearing the value and compiling my code. Note: If I manually rearrange the flags so the -U command follows, it will successfully compile as expected.

Should the platformio.ini build flags be passed last to rectify this issue?

Thanks for the great work so far!
-Patrick

[ivankravets]

PlatformIO passes all build_flags to Scons env.MergeFlags(flags). Looks like it doesn't support -U name option. I will contact with Scons developers and discuss it. If they say that env.MergeFlags doesn't parse -U, then I will implement own mechanism for this option.