bison-i18n: Ensure BISON_LOCALEDIR_c expands to a C string

[Bruno Haible]

Sam James reported that when configuring a package with --disable-nls,
not only BISON_LOCALEDIR expands to empty (which is acceptable since the
value is not used) but also BISON_LOCALEDIR_c expands to empty (which leads
to a C syntax error, see <https://savannah.gnu.org/bugs/?66533>).

This patch fixes it.


2024-12-04  Bruno Haible  <bruno@clisp.org>

        bison-i18n: Ensure BISON_LOCALEDIR_c expands to a C string.
        Reported by Holger Hoffstätte via Sam James <sam@gentoo.org>.
        * m4/bison-i18n.m4 (BISON_I18N): Define BISON_LOCALEDIR_c and
        BISON_LOCALEDIR_c_make in the usual way even when BISON_LOCALEDIR
        expands to empty.

diff --git a/m4/bison-i18n.m4 b/m4/bison-i18n.m4
index 3cf0848ca2..e5433a686a 100644
--- a/m4/bison-i18n.m4
+++ b/m4/bison-i18n.m4
@@ -1,5 +1,5 @@
 # bison-i18n.m4
-# serial 5
+# serial 6
 dnl Copyright (C) 2005-2006, 2009-2024 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -57,27 +57,28 @@ AC_DEFUN([BISON_I18N]
       fi
     fi
     AC_SUBST([BISON_LOCALEDIR])
+  fi
 
-    dnl Define BISON_LOCALEDIR_c and BISON_LOCALEDIR_c_make.
-    dnl Find the final value of BISON_LOCALEDIR.
-    gl_saved_prefix="${prefix}"
-    gl_saved_datarootdir="${datarootdir}"
-    gl_saved_localedir="${localedir}"
-    gl_saved_bisonlocaledir="${BISON_LOCALEDIR}"
-    dnl Unfortunately, prefix gets only finally determined at the end of
-    dnl configure.
-    if test "X$prefix" = "XNONE"; then
-      prefix="$ac_default_prefix"
-    fi
-    eval datarootdir="$datarootdir"
-    eval localedir="$localedir"
-    eval BISON_LOCALEDIR="$BISON_LOCALEDIR"
-    gl_BUILD_TO_HOST([BISON_LOCALEDIR])
-    BISON_LOCALEDIR="${gl_saved_bisonlocaledir}"
-    localedir="${gl_saved_localedir}"
-    datarootdir="${gl_saved_datarootdir}"
-    prefix="${gl_saved_prefix}"
+  dnl Define BISON_LOCALEDIR_c and BISON_LOCALEDIR_c_make.
+  dnl Find the final value of BISON_LOCALEDIR.
+  gl_saved_prefix="${prefix}"
+  gl_saved_datarootdir="${datarootdir}"
+  gl_saved_localedir="${localedir}"
+  gl_saved_bisonlocaledir="${BISON_LOCALEDIR}"
+  dnl Unfortunately, prefix gets only finally determined at the end of
+  dnl configure.
+  if test "X$prefix" = "XNONE"; then
+    prefix="$ac_default_prefix"
   fi
+  eval datarootdir="$datarootdir"
+  eval localedir="$localedir"
+  eval BISON_LOCALEDIR="$BISON_LOCALEDIR"
+  gl_BUILD_TO_HOST([BISON_LOCALEDIR])
+  BISON_LOCALEDIR="${gl_saved_bisonlocaledir}"
+  localedir="${gl_saved_localedir}"
+  datarootdir="${gl_saved_datarootdir}"
+  prefix="${gl_saved_prefix}"
+
   if test $BISON_USE_NLS = yes; then
     AC_DEFINE([YYENABLE_NLS], [1],
       [Define to 1 to internationalize bison runtime messages.])