diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index d8ca6d3dabd..69e3182ec32 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,12 @@
+2018-09-05  Tom Tromey  <tom@tromey.com>
+
+	* warning.m4 (AM_GDB_WARNINGS): Add -Wformat when testing
+	-Wformat-nonliteral.
+	* target-float.c (host_float_ops<T>::to_string)
+	(host_float_ops<T>::from_string): Use
+	DIAGNOSTIC_IGNORE_FORMAT_NONLITERAL.
+	* configure: Rebuild.
+
 2018-09-05  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* printcmd.c (printf_c_string): Use
diff --git a/gdb/configure b/gdb/configure
index 270657103b6..d92a256f1ff 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -15427,7 +15427,10 @@ case "${host}" in
     build_warnings="$build_warnings -Wno-unknown-pragmas"
     # Solaris 11 <unistd.h> marks vfork deprecated.
     build_warnings="$build_warnings -Wno-deprecated-declarations" ;;
-  *) build_warnings="$build_warnings -Wformat-nonliteral" ;;
+  *)
+    # Note that gcc requires -Wformat for -Wformat-nonliteral to work,
+    # but there's a special case for this below.
+    build_warnings="$build_warnings -Wformat-nonliteral" ;;
 esac
 
 # Check whether --enable-build-warnings was given.
@@ -15483,6 +15486,12 @@ $as_echo_n "checking compiler warning flags... " >&6; }
 	case $w in
 	-Wno-*)
 		wtest=`echo $w | sed 's/-Wno-/-W/g'` ;;
+        -Wformat-nonliteral)
+		# gcc requires -Wformat before -Wformat-nonliteral
+		# will work, so stick them together.
+		w="-Wformat $w"
+		wtest="$w"
+		;;
 	*)
 		wtest=$w ;;
 	esac
diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index cd0318c79aa..0c5c32b22ef 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,7 @@
+2018-09-05  Tom Tromey  <tom@tromey.com>
+
+	* configure: Rebuild.
+
 2018-08-28  Simon Marchi  <simon.marchi@polymtl.ca>
 
 	PR build/23399
diff --git a/gdb/gdbserver/configure b/gdb/gdbserver/configure
index 7454cd8ad37..f5cbbaea78a 100755
--- a/gdb/gdbserver/configure
+++ b/gdb/gdbserver/configure
@@ -7258,7 +7258,10 @@ case "${host}" in
     build_warnings="$build_warnings -Wno-unknown-pragmas"
     # Solaris 11 <unistd.h> marks vfork deprecated.
     build_warnings="$build_warnings -Wno-deprecated-declarations" ;;
-  *) build_warnings="$build_warnings -Wformat-nonliteral" ;;
+  *)
+    # Note that gcc requires -Wformat for -Wformat-nonliteral to work,
+    # but there's a special case for this below.
+    build_warnings="$build_warnings -Wformat-nonliteral" ;;
 esac
 
 # Check whether --enable-build-warnings was given.
@@ -7314,6 +7317,12 @@ $as_echo_n "checking compiler warning flags... " >&6; }
 	case $w in
 	-Wno-*)
 		wtest=`echo $w | sed 's/-Wno-/-W/g'` ;;
+        -Wformat-nonliteral)
+		# gcc requires -Wformat before -Wformat-nonliteral
+		# will work, so stick them together.
+		w="-Wformat $w"
+		wtest="$w"
+		;;
 	*)
 		wtest=$w ;;
 	esac
diff --git a/gdb/target-float.c b/gdb/target-float.c
index c2878cb0a08..a12f216b53d 100644
--- a/gdb/target-float.c
+++ b/gdb/target-float.c
@@ -948,7 +948,11 @@ host_float_ops<T>::to_string (const gdb_byte *addr, const struct type *type,
 
   T host_float;
   from_target (type, addr, &host_float);
+
+  DIAGNOSTIC_PUSH
+  DIAGNOSTIC_IGNORE_FORMAT_NONLITERAL
   return string_printf (host_format.c_str (), host_float);
+  DIAGNOSTIC_POP
 }
 
 /* Parse string IN into a target floating-number of type TYPE and
@@ -977,7 +981,10 @@ host_float_ops<T>::from_string (gdb_byte *addr, const struct type *type,
     scan_format += scanf_length_modifier<T>::value;
   scan_format += "g%n";
 
+  DIAGNOSTIC_PUSH
+  DIAGNOSTIC_IGNORE_FORMAT_NONLITERAL
   num = sscanf (in.c_str (), scan_format.c_str(), &host_float, &n);
+  DIAGNOSTIC_POP
 
   /* The sscanf man page suggests not making any assumptions on the effect
      of %n on the result, so we don't.
diff --git a/gdb/warning.m4 b/gdb/warning.m4
index dd338493f9e..82170acc802 100644
--- a/gdb/warning.m4
+++ b/gdb/warning.m4
@@ -58,7 +58,10 @@ case "${host}" in
     build_warnings="$build_warnings -Wno-unknown-pragmas"
     # Solaris 11 <unistd.h> marks vfork deprecated.
     build_warnings="$build_warnings -Wno-deprecated-declarations" ;;
-  *) build_warnings="$build_warnings -Wformat-nonliteral" ;;
+  *)
+    # Note that gcc requires -Wformat for -Wformat-nonliteral to work,
+    # but there's a special case for this below.
+    build_warnings="$build_warnings -Wformat-nonliteral" ;;
 esac
 
 AC_ARG_ENABLE(build-warnings,
@@ -106,6 +109,12 @@ then
 	case $w in
 	-Wno-*)
 		wtest=`echo $w | sed 's/-Wno-/-W/g'` ;;
+        -Wformat-nonliteral)
+		# gcc requires -Wformat before -Wformat-nonliteral
+		# will work, so stick them together.
+		w="-Wformat $w"
+		wtest="$w"
+		;;
 	*)
 		wtest=$w ;;
 	esac