Read-ahead code introduced in the r313332 contains "the end of cache marker" which I believe superfluous, as cache is allocated on heap and there is already a similar code in the malloc()/free() to detect data corruption and panic:
$ grep USEENDGUARD /usr/src/stand/libsa/*.[ch] /usr/src/stand/libsa/zalloc_defs.h:#define USEENDGUARD /usr/src/stand/libsa/zalloc_malloc.c:#ifdef USEENDGUARD /usr/src/stand/libsa/zalloc_malloc.c:#ifdef USEENDGUARD /usr/src/stand/libsa/zalloc_malloc.c:#ifdef USEENDGUARD
I believe that code is more "correct" since such incidents should not be taken lightly as often loader logs are not easily available and or often looked upon. Merely issuing a warning when condition is detected is not sufficient since allowing system to continue bootstrap is likely to cause a subsequent kernel crash/misbehaviour that would be really hard to debug and can lead to a severe data corruption as well.