shf_sopen
shf_sopen(buf, bsize, SHF_WR, &shf);
shf_sopen(NULL, 0, SHF_WR|SHF_DYNAMIC, &shf);
struct shf *shf_sopen(char *, int, int, struct shf *);
shf_sopen(s, n, SHF_WR | (s ? 0 : SHF_DYNAMIC), &shf);
shf_sopen(NULL, 32, SHF_WR | SHF_DYNAMIC, &shf);