diff -r 19af679e3b3c lib/libc/compat/gen/compat_frexp_ieee754.c
--- a/lib/libc/compat/gen/compat_frexp_ieee754.c	Tue May 05 04:32:59 2020 +0000
+++ b/lib/libc/compat/gen/compat_frexp_ieee754.c	Tue May 05 22:07:11 2020 +0000
@@ -44,10 +44,18 @@ static char sccsid[] = "@(#)frexp.c	8.1 
 #endif
 #endif /* LIBC_SCCS and not lint */
 
+#include "namespace.h"
+
 #include <sys/types.h>
+
 #include <machine/ieee.h>
 
-double frexp(double, int *);
+#include <math.h>
+
+__weak_alias(frexp,_frexp)
+__warn_references(frexp,
+    "warning: reference to compatibility frexp();"
+    " link with -lm for correct reference")
 
 /*
  * Split the given value into a fraction in the range [0.5, 1.0) and
diff -r 19af679e3b3c lib/libc/compat/gen/compat_ldexp_ieee754.c
--- a/lib/libc/compat/gen/compat_ldexp_ieee754.c	Tue May 05 04:32:59 2020 +0000
+++ b/lib/libc/compat/gen/compat_ldexp_ieee754.c	Tue May 05 22:07:11 2020 +0000
@@ -34,11 +34,19 @@
 __RCSID("$NetBSD: compat_ldexp_ieee754.c,v 1.7 2016/08/27 09:35:13 christos Exp $");
 #endif /* LIBC_SCCS and not lint */
 
+#include "namespace.h"
+
 #include <sys/types.h>
+
 #include <machine/ieee.h>
+
 #include <errno.h>
+#include <math.h>
 
-double ldexp(double, int);
+__weak_alias(ldexp,_ldexp)
+__warn_references(ldexp,
+    "warning: reference to compatibility ldexp();"
+    " link with -lm for correct reference")
 
 /*
  * Multiply the given value by 2^expon.
diff -r 19af679e3b3c lib/libc/compat/gen/compat_modf_ieee754.c
--- a/lib/libc/compat/gen/compat_modf_ieee754.c	Tue May 05 04:32:59 2020 +0000
+++ b/lib/libc/compat/gen/compat_modf_ieee754.c	Tue May 05 22:07:11 2020 +0000
@@ -27,11 +27,24 @@
  * rights to redistribute these changes.
  */
 
+#include <sys/cdefs.h>
+#if defined(LIBC_SCCS) && !defined(lint)
+__RCSID("$NetBSD$");
+#endif /* LIBC_SCCS and not lint */
+
+#include "namespace.h"
+
 #include <sys/types.h>
+
 #include <machine/ieee.h>
+
 #include <errno.h>
+#include <math.h>
 
-double modf(double, double *);
+__weak_alias(modf,_modf)
+__warn_references(modf,
+    "warning: reference to compatibility modf();"
+    " link with -lm for correct reference")
 
 /*
  * double modf(double val, double *iptr)
diff -r 19af679e3b3c lib/libc/include/namespace.h
--- a/lib/libc/include/namespace.h	Tue May 05 04:32:59 2020 +0000
+++ b/lib/libc/include/namespace.h	Tue May 05 22:07:11 2020 +0000
@@ -49,6 +49,7 @@
 #define fileno		_fileno
 #endif /* _REENTRANT */
 #define fork		_fork
+#define frexp		_frexp
 #define fseeko		_fseeko
 #define ftello		_ftello
 #define getcontext	_getcontext
@@ -57,6 +58,8 @@
 #define imaxdiv		_imaxdiv
 #define inet_aton	_inet_aton
 #define inet_pton	_inet_pton
+#define ldexp		_ldexp
+#define modf		_modf
 #define pipe		_pipe
 #define sbrk		_sbrk
 #define strerror_l	_strerror_l