The VM harness (tests/vm/) builds and exercises the tools on real Debian and Alpine guests, driving the serial console (no sshd/cloud-init dependency). Results on Debian 12 (glibc 2.36, gcc 12.2): 12/12 checks pass, 0 warnings with -Wall -Wextra, including a real 128M -> 256M resize and the rollback save/restore/reject paths. Results on Alpine 3.20 (musl 1.2.5): the build cannot start. configure stops at "reiserfsprogs requires a method to add printf modifiers" because reiserfscore/prints.c depends on glibc's register_printf_specifier(3) and <printf.h>, which musl does not provide. This is pre-existing and out of scope here; measured at 341 use sites across 20+ files, all routed through reiserfs_warning()/reiserfs_info(). Documented in tests/vm/RESULTS.md. Fix the one real defect the harness surfaced: fsck/semantic_check.c: check_check_regular_file() is called with NULL for new_ih (line 466), so the block that would fill *new_ih is unreachable and check_semantic_pass() never returns RELOCATED through that path. The "case RELOCATED:" arm still reads relocated_ih.ih_key, which gcc 12.2 reports as "may be used uninitialized" (-Wmaybe-uninitialized); gcc 16 does not, because it proves the path dead. Zero-initialise the struct and say why. Verified: 0 warnings on gcc 12.2 after the change, and the Debian battery stays at 12/12.