sh-quote: make C++ safe

[Bruno Haible]

A trivial adjustment to support C++, and to avoid gcc warnings in case
sh-quote.h gets included twice.


2012-05-08  Bruno Haible  <address@hidden>

        sh-quote: Make C++ safe and allow multiple inclusion.
        * lib/sh-quote.h: Add double-inclusion guard. For C++, wrap function
        declarations in extern "C".

--- lib/sh-quote.h.orig Wed May  9 03:20:04 2012
+++ lib/sh-quote.h      Wed May  9 00:35:41 2012
@@ -15,12 +15,19 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
+#ifndef _SH_QUOTE_H
+#define _SH_QUOTE_H
+
 /* When passing a command to a shell, we must quote the program name and
    arguments, since Unix shells interpret characters like " ", "'", "<", ">",
    "$" etc. in a special way.  */
 
 #include <stddef.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* Returns the number of bytes needed for the quoted string.  */
 extern size_t shell_quote_length (const char *string);
 
@@ -34,3 +41,9 @@
 /* Returns a freshly allocated string containing all argument strings, quoted,
    separated through spaces.  */
 extern char * shell_quote_argv (char * const *argv);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _SH_QUOTE_H */