Editing PsionLX (section)

=== Building it ===

The netBook Pro's userspace uses the old ARM ABI (OABI, ELF flags <code>0x00000002</code>), which no current cross-compiler produces. The reconstruction therefore compiles natively inside an emulated ARM machine: a Debian etch <code>arm</code> root filesystem, assembled from 66 packages from archive.debian.org (GCC 4.1, binutils 2.17, glibc 2.3.6), booted under <code>qemu-system-arm -M versatilepb</code>, whose ARM926EJ-S core is close enough to the PXA255's ARMv5TE for the output to run on the device.<ref name="rtc-docs" />

* C++ programs are built with GCC 3.4. The device carries <code>libstdc++.so.6.0.3</code>, which is GCC 3.4's runtime; GCC 4 output compiles and links but needs a newer library than the device has.
* Headers are taken, library by library, from the exact versions on the device (libgpewidget 0.97, libeventdb 0.15, libschedule 0.14 and others), because the build environment's newer GPE headers declared functions with different arguments.
* Before any program is installed it must pass three checks against the image itself: OABI ELF flags, every needed library present, and every undefined dynamic symbol defined somewhere in that set. Weak symbols that every GCC binary leaves unresolved, such as <code>__gmon_start__</code>, are ignored.

Psion's recipes are read by a script that takes the newest recipe for a package, collects every <code>SRC_URI</code> form including <code>SRC_URI +=</code> and included files, fetches the pinned release and applies Psion's patches in order at the level each declares. With the exact release tarballs, all of Psion's GPE patches applied except one hunk of gpe-bluetooth's <code>change-sdp-to-bluetooth.patch</code>, which swaps <code>-lsdp</code> for <code>-lbluetooth</code> in a link line that differs in the released tarball. That change was made by hand.<ref name="rtc-docs" />