Hashed library builds - environment variables

[frankdownunder]

With regard to to hashed library builds - #1724, I noticed the following sllghtly quirky thing:
cd Basic_Blink
export SMING_ARCH=Host
make
export SMING_ARCH=Esp8266
make

I would have expected the second invocation of make to use the different Arch setting. Passing it on the command line works as expected.

[mikee47]

If you haven't found Sming/building.md have a read, hopefully make things clearer.

This behaviour is by design. Cached variables always take priority over the environment (including project makefile / component.mk settings and Eclipse). Some advantages:

• Switching between eclipse and CLI is simpler because they'll use the same settings, regardless of what's been set elsewhere.
• Variables are stored with each project (and build type)
• If computer is rebooted, crashes, etc. you can get straight back to where you were without having to run a load of exports.

To get your example to work, do this:

cd Basic_Blink
export SMING_ARCH=Host
make
export SMING_ARCH=Esp8266
make config-clean
make

but the easier way is:

cd Basic_Blink
make SMING_ARCH=Host
make SMING_ARCH=Esp8266

And you don't have to set the variables every time you run the command. See make list-config.