https://bugs.gentoo.org/661508

--- a/configure
+++ b/configure
@@ -638,6 +638,8 @@
 IS_CROSS_COMPILE_FALSE
 IS_CROSS_COMPILE_TRUE
 LIBOBJS
+HAVE_VISIBILITY
+CFLAG_VISIBILITY
 OTOOL64
 OTOOL
 LIPO
@@ -12512,7 +12519,92 @@
 # Only expand once:
 
 
-gl_VISIBILITY
+
+
+  CFLAG_VISIBILITY=
+  HAVE_VISIBILITY=0
+  if test -n "$GCC"; then
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether the -Werror option is usable" >&5
+$as_echo_n "checking whether the -Werror option is usable... " >&6; }
+    if ${gl_cv_cc_vis_werror+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+      gl_save_CFLAGS="$CFLAGS"
+      CFLAGS="$CFLAGS -Werror"
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  gl_cv_cc_vis_werror=yes
+else
+  gl_cv_cc_vis_werror=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+      CFLAGS="$gl_save_CFLAGS"
+fi
+
+    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $gl_cv_cc_vis_werror" >&5
+$as_echo "$gl_cv_cc_vis_werror" >&6; }
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for simple visibility declarations" >&5
+$as_echo_n "checking for simple visibility declarations... " >&6; }
+    if ${gl_cv_cc_visibility+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+      gl_save_CFLAGS="$CFLAGS"
+      CFLAGS="$CFLAGS -fvisibility=hidden"
+                                    if test $gl_cv_cc_vis_werror = yes; then
+        CFLAGS="$CFLAGS -Werror"
+      fi
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+extern __attribute__((__visibility__("hidden"))) int hiddenvar;
+             extern __attribute__((__visibility__("default"))) int exportedvar;
+             extern __attribute__((__visibility__("hidden"))) int hiddenfunc (void);
+             extern __attribute__((__visibility__("default"))) int exportedfunc (void);
+             void dummyfunc (void) {}
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  gl_cv_cc_visibility=yes
+else
+  gl_cv_cc_visibility=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+      CFLAGS="$gl_save_CFLAGS"
+fi
+
+    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $gl_cv_cc_visibility" >&5
+$as_echo "$gl_cv_cc_visibility" >&6; }
+    if test $gl_cv_cc_visibility = yes; then
+      CFLAG_VISIBILITY="-fvisibility=hidden"
+      HAVE_VISIBILITY=1
+    fi
+  fi
+
+
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_VISIBILITY $HAVE_VISIBILITY
+_ACEOF
+
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ANSI C header files" >&5
 $as_echo_n "checking for ANSI C header files... " >&6; }
 if ${ac_cv_header_stdc+:} false; then :
@@ -16194,7 +16286,7 @@
     DEPDIR=`sed -n 's/^DEPDIR = //p' < "$mf"`
     test -z "$DEPDIR" && continue
     am__include=`sed -n 's/^am__include = //p' < "$mf"`
-    test -z "am__include" && continue
+    test -z "$am__include" && continue
     am__quote=`sed -n 's/^am__quote = //p' < "$mf"`
     # Find all dependency output files, they are included files with
     # $(DEPDIR) in their names.  We invoke sed twice because it is the