+2018-07-22  Simon Marchi  <simon.marchi@polymtl.ca>
+           Tom Tromey  <tom@tromey.com>
+
+       * warning.m4 (AM_GDB_WARNINGS): Add -Wunused-variable and special
+       test for it.
+       * configure: Rebuild.
+
 2018-07-22  Tom Tromey  <tom@tromey.com>
 
        * regformats/regdat.sh: Define xmltarget_${name} inside
 
 
 # The options we'll try to enable.
 build_warnings="-Wall -Wpointer-arith \
--Wno-unused -Wunused-value -Wunused-function \
+-Wno-unused -Wunused-value -Wunused-variable -Wunused-function \
 -Wno-switch -Wno-char-subscripts \
 -Wempty-body -Wunused-but-set-parameter -Wunused-but-set-variable \
 -Wno-sign-compare -Wno-narrowing -Wno-error=maybe-uninitialized \
            CFLAGS="$CFLAGS -Werror $wtest"
            saved_CXXFLAGS="$CXXFLAGS"
            CXXFLAGS="$CXXFLAGS -Werror $wtest"
-           cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+           if test "x$w" = "x-Wunused-variable"; then
+             # Check for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38958,
+             # fixed in GCC 4.9.  This test is derived from the gdb
+             # source code that triggered this bug in GCC.
+             cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+struct scoped_restore_base {};
+                 struct scoped_restore_tmpl : public scoped_restore_base {
+                  ~scoped_restore_tmpl() {}
+                };
+int
+main ()
+{
+const scoped_restore_base &b = scoped_restore_tmpl();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  WARN_CFLAGS="${WARN_CFLAGS} $w"
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+           else
+             cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
 int
   WARN_CFLAGS="${WARN_CFLAGS} $w"
 fi
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+           fi
            CFLAGS="$saved_CFLAGS"
            CXXFLAGS="$saved_CXXFLAGS"
        esac
 
+2018-07-22  Tom Tromey  <tom@tromey.com>
+
+       * configure: Rebuild.
+
 2018-07-22  Tom Tromey  <tom@tromey.com>
 
        * win32-low.c (win32_create_inferior): Remove unused variables.
 
 
 # The options we'll try to enable.
 build_warnings="-Wall -Wpointer-arith \
--Wno-unused -Wunused-value -Wunused-function \
+-Wno-unused -Wunused-value -Wunused-variable -Wunused-function \
 -Wno-switch -Wno-char-subscripts \
 -Wempty-body -Wunused-but-set-parameter -Wunused-but-set-variable \
 -Wno-sign-compare -Wno-narrowing -Wno-error=maybe-uninitialized \
            CFLAGS="$CFLAGS -Werror $wtest"
            saved_CXXFLAGS="$CXXFLAGS"
            CXXFLAGS="$CXXFLAGS -Werror $wtest"
-           cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+           if test "x$w" = "x-Wunused-variable"; then
+             # Check for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38958,
+             # fixed in GCC 4.9.  This test is derived from the gdb
+             # source code that triggered this bug in GCC.
+             cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+struct scoped_restore_base {};
+                 struct scoped_restore_tmpl : public scoped_restore_base {
+                  ~scoped_restore_tmpl() {}
+                };
+int
+main ()
+{
+const scoped_restore_base &b = scoped_restore_tmpl();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  WARN_CFLAGS="${WARN_CFLAGS} $w"
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+           else
+             cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
 int
   WARN_CFLAGS="${WARN_CFLAGS} $w"
 fi
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+           fi
            CFLAGS="$saved_CFLAGS"
            CXXFLAGS="$saved_CXXFLAGS"
        esac
 
 
 # The options we'll try to enable.
 build_warnings="-Wall -Wpointer-arith \
--Wno-unused -Wunused-value -Wunused-function \
+-Wno-unused -Wunused-value -Wunused-variable -Wunused-function \
 -Wno-switch -Wno-char-subscripts \
 -Wempty-body -Wunused-but-set-parameter -Wunused-but-set-variable \
 -Wno-sign-compare -Wno-narrowing -Wno-error=maybe-uninitialized \
            CFLAGS="$CFLAGS -Werror $wtest"
            saved_CXXFLAGS="$CXXFLAGS"
            CXXFLAGS="$CXXFLAGS -Werror $wtest"
-           AC_TRY_COMPILE([],[],WARN_CFLAGS="${WARN_CFLAGS} $w",)
+           if test "x$w" = "x-Wunused-variable"; then
+             # Check for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38958,
+             # fixed in GCC 4.9.  This test is derived from the gdb
+             # source code that triggered this bug in GCC.
+             AC_TRY_COMPILE(
+               [struct scoped_restore_base {};
+                 struct scoped_restore_tmpl : public scoped_restore_base {
+                  ~scoped_restore_tmpl() {}
+                };],
+               [const scoped_restore_base &b = scoped_restore_tmpl();],
+               WARN_CFLAGS="${WARN_CFLAGS} $w",)
+           else
+             AC_TRY_COMPILE([],[],WARN_CFLAGS="${WARN_CFLAGS} $w",)
+           fi
            CFLAGS="$saved_CFLAGS"
            CXXFLAGS="$saved_CXXFLAGS"
        esac