UDB_HEADER_SIZE
if(g.hsize < UDB_HEADER_SIZE) {
if(g.hsize > UDB_HEADER_SIZE) {
if(g.fsize < UDB_HEADER_SIZE || g.fsize < g.hsize) {
g->hsize = UDB_HEADER_SIZE;
g->fsize = UDB_HEADER_SIZE;
uint64_t endsize = UDB_HEADER_SIZE;
assert(UDB_HEADER_SIZE % UDB_ALLOC_CHUNK_MINSIZE == 0);
a->nextgrow = UDB_HEADER_SIZE;