strsvisx
int strsvisx(char *, const char *, size_t, int, const char *);
strsvisx(visbuf, buf, size, VIS_TAB|VIS_NL|VIS_OCTAL, "\"");
ATF_REQUIRE(strsvisx(visbuf, srcbuf, SIZE, styles[i], "") > 0);
return (strsvisx(buf, data, len, visflags, extra_echars));