+ if (fmt == &floatformat_i387_ext)
+ {
+ /* In the i387 double-extended format, if the exponent is all
+ ones, then the integer bit must be set. If the exponent
+ is neither 0 nor ~0, the intbit must also be set. Only
+ if the exponent is zero can it be zero, and then it must
+ be zero. */
+ unsigned int exponent, int_bit;
+ unsigned char *ufrom = (unsigned char *) from;
+
+ exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize,
+ fmt->exp_start, fmt->exp_len);
+ int_bit = get_field (ufrom, fmt->byteorder, fmt->totalsize,
+ fmt->man_start, 1);
+
+ if ((exponent == 0) != (int_bit == 0))
+ return 0;
+ else
+ return 1;
+ }
+
+ /* Other formats with invalid representations should be added
+ here. */
+ return 1;
}