cross_reference --platform listed core files the platform's launcher already settles, as Batocera's DuckStation scph1002a.bin while the PAL slot holds scph5502.bin. It now hands the launcher layer the same entries verify does, and counts what it settles as set aside.
A links record naming a file is where the emulator reads it: ROCKNIX links /storage/roms/bios/nds_bios_arm9.bin into DraStic's system folder (start_drastic.sh:37-41). $biosdir, ${biosPath} and $bios_path are the BIOS directory as RetroPie, EmuDeck and RetroDECK write it, and every place of those platforms was dropped as an unknown folder. A core name the launcher replaces is no longer packed when held: EmuDeck passes Complex_4627v1.03.bin to xemu (emuDeckXemu.sh:60-61), which never opens Complex_4627.bin.
NanoBoyAdvance opens general.bios_path, default bios.bin (src/platform/core/src/config.cpp:36 at 3bb6f478). gba_bios.bin is the path ROCKNIX's config.toml sets, recorded under launchers: in rocknix.yml.
Without the alias the entry met only PCem's and QEMU's bios.bin, 64 and 128 KB, which BIOSLoader refuses (bios.cpp:17-48). verify counted it held by name, so the launcher layer left it alone and the ROCKNIX pack gained PCem's image. A hashless entry whose every same-named copy fails its size is now not held, and the gba_bios.bin ROCKNIX declares settles it.
EmuDeck passes Complex_4627v1.03.bin as xemu's flash ROM
(emuDeckXemu.sh:60-61), and xemu's entry Complex_4627.bin states no hash,
only the sizes it maps. The layer matched entries by name or content
only, so without the alias the default name was still asked for. A
hashless entry that checks a size now takes a launcher file of a size
it accepts, when no other entry of that core accepts that size too.
The launcher layer packed a file under the launcher's name whatever the
platform installs: ROCKNIX's xemu config reads hdd/xbox_hdd.qcow2, and
the profile marks that image installed_on rocknix, yet the pack brought
one. A place whose entry the emulator installs on that platform is now
filled by the install, as validation.deliverable has it for the pack.
A names_searched list is one place the launcher fills with the first name it finds, so a core file it would never open once another name of the list is held is not reported missing. A place no declared file and no packed core file fills receives, under the launcher's name, a file the core accepts by content. The layer is applied inside find_undeclared_files, which verify and the pack builder both read, and a test reads their source to keep it there.
Abdessamad Derraz