-# if !defined _LIBICONV_VERSION && (defined sgi || defined __sgi)
- /* Irix iconv() inserts a NUL byte if it cannot convert. */
+# if !defined _LIBICONV_VERSION && !defined __GLIBC__
+ /* Irix iconv() inserts a NUL byte if it cannot convert.
+ NetBSD iconv() inserts a question mark if it cannot convert.
+ Only GNU libiconv and GNU libc are known to prefer to fail rather
+ than doing a lossy conversion. */