AC_CHECK_HEADERS(unistr.h,

[AC_CHECK_LIB([unistring], [u8_strlen], [ UNISTRING_LIBS="-lunistring" ], [AC_MSG_ERROR([No usable libunistring library found])])],

[AC_MSG_ERROR([libunistring header files are not installed])]

)

AC_CHECK_HEADERS(unicase.h,

[AC_CHECK_LIB([unistring], [u8_casecmp], [ UNISTRING_LIBS="-lunistring" ], [AC_MSG_ERROR([No usable libunistring library found])])],

[AC_MSG_ERROR([libunistring header files are not installed])]

)