I have added the #ifdef __CYGWIN32__ to modify the fmt_fp.c

src/fmt_fp.c

@@ -90,11 +90,13 @@ fmt_u(uint32_t x, char *s)
 typedef char compiler_defines_long_double_incorrectly[9-(int)sizeof(long double)];
 #endif
 
+#ifdef __CYGWIN32__
 static long double
 frexpl (long double x, int *eptr)
 {
 	return frexp(x, eptr);
 }
+#endif
 
 static int
 fmt_fp(struct fmt_args *f, long double y, int w, int p, int fl, int t)