If the public objects file is not writable by the user (which is the way it should be) you get a permission denied error when running export_c_structs to generate the c_structs.h file:
$ make
make -C gnu
make[1]: Entering directory `/pub/objectify/gnu'
make[1]: Nothing to be done for `all'.
make[1]: Leaving directory `/pub/objectify/gnu'
cp -p gnu/md5.o .
cp -p gnu/sha1.o .
gcc -Wall -O3 -D_FILE_OFFSET_BITS=64 -DUSE_PREDEFINED_STRUCTS -DNO_BACKUP -DPUBLIC_MODE \
-o export_c_structs export_c_structs.c objectify.c disk_io.c reference_list.c time_stamp.c \
crc32.c log.c class_definition.c name.c spelling.c security.c user_config.c \
-lrt -lcrypto
./export_c_structs > c_structs.h
/usr/local/share/objectify/public.obj: Permission denied
make: *** [c_structs.h] Error 1
Logged In: YES
user_id=113600
Originator: YES
Fixed in Alpha_28.2.