libwally: enforce optimize for size

[NickeZ]

libwally was compiling with -03. no bueno.

old:
   text    data     bss     dec     hex filename
 452980   22924  208352  684256   a70e0 firmware.elf

new:
   text    data     bss     dec     hex filename
 443532   22932  208352  674816   a4c00 firmware.elf

[benma]

libwally is the lib which performs the slow bip39 unlock, and also ships secp256k1. did you check if unlock does not take longer, and that signing a tx works?

[benma]

This is very not nice :D Is there really no way to configure it or pass it as an env var or sth?

otherwise you can also make a new branch here: https://github.com/shiftdevices/libwally-core

[NickeZ]

• I'll have to check that libwally operations don't take significantly longer.
• It isn't possible to change the optimization flags for libwally, they have only 2 options, debug -Og and non-debug -O3.
• Using -O3 in general is absolute madness. They should be using -O2. -O3 enables new and exciting optimizations which hasn't been battle tested. It is well known to sometimes pessimize code.

I'll patch our fork of libwally instead of monkeypatching like this though..

[benma]

In this case I suggest to fix it upstream, and not do this change for now. Seems a bit premature, we are not strapped for space yet.

[NickeZ]

Solved upstream: ElementsProject/libwally-core#182

They agreed that -O3 is wrong and overriding the user is wrong. So now it is possible to set optimization level with CFLAGS.

[x1ddos]

Solved upstream: ElementsProject/libwally-core#182

Still need to pull it in and update commit hash in https://github.com/digitalbitbox/bitbox02-firmware/tree/master/external, right.

Also, would be nice if url entries in https://github.com/digitalbitbox/bitbox02-firmware/blob/26a8b821aad9814007b9ff5dacf043f8883ced70/.gitmodules were updated to point to github/digitalbitbox/repo instead of shiftdevices.

[NickeZ]

Sure, but both those things are unrelated to this PR. Make comments / create issues instead.