[SOLVED] Crossdev for arm-none-eabi and specifying ARM CPUs

[jannis]

Since some time I'm toying around with Raspberry Pi's Pico board. The SoC has two ARM Cortex-M0+ cores and the "Getting started" document (https://datasheets.raspberrypi.org/pico ... h-pico.pdf) is pretty Ubuntu focused and thus assumes the binary toolchain. I thought I can do better with Gentoo and crossdev and emerged the toolchain for target arm-none-eabi. Generally, it's all working fine, until recently a specific program made the Pico board crash. I debugged it to being the "strcmp" function leading to an exception in the CPU. In the RaspberryPi Forums, I suspected the toolchain and this was also assumed to be the case by others: https://www.raspberrypi.org/forums/view ... 3#p1856673.
During the compilation of cross-arm-none-eabi/newlib, I can see that several variants are being built, tuned for several ARM instruction sets, including v5te and v7+fp. According to https://en.wikipedia.org/wiki/ARM_Corte ... ction_sets, the M0+ should have ARMv6-M architecture without FP.

I know very well how to tune my host compiler and Gentoo system for my specific host CPU but I'm a bit lost when it comes to tuning cross-arm-none-eabi/newlib for the Cortex-M0+ or actually making sure the toolchain doesn't emit instructions that are simply not supported by the chip, as it seems to be the case for strcmp.

I've had a look at /usr/arm-none-eabi/etc/portage/make.conf, /var/db/repos/localrepo-crossdev/cross-arm-none-eabi/newlib/newlib-4.1.0.ebuild and the "toolchain-funcs" eclass it uses but I could not find references to the v5te and v7+fp architectures being actually created.

[jannis]

Oh, and I've seen https://wiki.gentoo.org/wiki/ARM#Enable ... at_support as well. To me it looks like this is rather aimed at gcc instead of newlib but I will give it a try nevertheless

[jannis]

Re-creating the crossdev ebuilds, there is this warning that I've just read now:

!!! WARNING - Cannot auto-configure CHOST arm-none-eabi;
!!! You should edit /usr/arm-none-eabi/etc/portage/make.conf /usr/arm-none-eabi/etc/portage/profile/make.defaults /usr/arm-none-eabi/etc/portage/profile/use.force
!!! by hand to complete your configuration.

I've modified the CFLAGS and CXXFLAGS in /usr/arm-none-eabi/etc/portage/make.conf and will see how that goes. Currently compiling

[jannis]

Okay, I thought it wouldn't make a difference since the buildlog of cross-arm-none-eabi/newlib looked exactly the same and also the files installed also are the same (including the v5te and v7+fpu folders). But this time, the program for the Pico board compiled by the toolchain actually works