diff --git a/autogen/config.in b/autogen/config.in
index 10969fd99c2..99074bd1bc5 100644
--- a/autogen/config.in
+++ b/autogen/config.in
@@ -246,9 +246,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 /* Define to 1 if strtold conforms to C99. */
 #undef HAVE_C99_STRTOLD
 
-/* Define to 1 if you have the `cbrt' function. */
-#undef HAVE_CBRT
-
 /* Define to 1 if you have the `cfmakeraw' function. */
 #undef HAVE_CFMAKERAW
 
@@ -638,9 +635,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 /* Define to 1 if you have the `localtime_r' function. */
 #undef HAVE_LOCALTIME_R
 
-/* Define to 1 if you have the `logb' function. */
-#undef HAVE_LOGB
-
 /* Define to 1 if you support file names longer than 14 characters. */
 #undef HAVE_LONG_FILE_NAMES
 
diff --git a/autogen/configure b/autogen/configure
index 3621eee77c6..5f4013e4b88 100755
--- a/autogen/configure
+++ b/autogen/configure
@@ -12926,8 +12926,8 @@ $as_echo "#define HAVE_H_ERRNO 1" >>confdefs.h
 
 fi
 
-# fmod, logb, and frexp are found in -lm on most systems.
-# On HPUX 9.01, -lm does not contain logb, so check for sqrt.
+# sqrt and other floating-point functions such as fmod and frexp
+# are found in -lm on most systems.
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sqrt in -lm" >&5
 $as_echo_n "checking for sqrt in -lm... " >&6; }
 if test "${ac_cv_lib_m_sqrt+set}" = set; then :
@@ -13177,7 +13177,7 @@ esac
 
 for ac_func in gethostname \
 closedir getrusage get_current_dir_name \
-lrand48 logb cbrt setsid \
+lrand48 setsid \
 fpathconf select euidaccess getpagesize setlocale \
 utimes getrlimit setrlimit setpgid getcwd shutdown getaddrinfo \
 __fpending strsignal setitimer \