ArchiveLookup: return const strings

src/ArchiveLookup.cxx

@@ -29,7 +29,9 @@
 #include <unistd.h>
 #include <errno.h>
 
-bool archive_lookup(char *pathname, char **archive, char **inpath, char **suffix)
+bool
+archive_lookup(char *pathname, const char **archive,
+	       const char **inpath, const char **suffix)
 {
 	char *pathdupe;
 	int len, idx;

src/ArchiveLookup.hxx

@@ -37,7 +37,9 @@
  * inarchive pathname:		Talco - Combat Circus/12 - A la pachenka.mp3
  * and suffix:			 zip
  */
-bool archive_lookup(char *pathname, char **archive, char **inpath, char **suffix);
+bool
+archive_lookup(char *pathname, const char **archive,
+	       const char **inpath, const char **suffix);
 
 #endif
 

src/input/ArchiveInputPlugin.cxx

@@ -45,14 +45,14 @@ input_archive_open(const char *pathname,
 		   Error &error)
 {
 	const struct archive_plugin *arplug;
-	char *archive, *filename, *suffix, *pname;
 	struct input_stream *is;
 
 	if (!Path::IsAbsoluteFS(pathname))
 		return NULL;
 
-	pname = g_strdup(pathname);
+	char *pname = g_strdup(pathname);
 	// archive_lookup will modify pname when true is returned
+	const char *archive, *filename, *suffix;
 	if (!archive_lookup(pname, &archive, &filename, &suffix)) {
 		FormatDebug(archive_domain,
 			    "not an archive, lookup %s failed", pname);