xenpmd.c: use dynamic allocation

On NetBSD, d_name is larger than 256, so file_name[284] may not be large
enough (and gcc emits a format-truncation error).
Use asprintf() instead of snprintf() on a static on-stack buffer.

Signed-off-by: Manuel Bouyer <bouyer@netbsd.org>
Reviewed-by: Ian Jackson <ian.jackson@eu.citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Release-Acked-by: Ian Jackson <iwj@xenproject.org>

Plus

define GNU_SOURCE for asprintf()

Harmless on NetBSD.

Signed-off-by: Manuel Bouyer <bouyer@netbsd.org>
Reviewed-by: Ian Jackson <ian.jackson@eu.citrix.com>
Release-Acked-by: Ian Jackson <iwj@xenproject.org>

tools/xenpmd/xenpmd.c

@@ -32,6 +32,7 @@
  * passed to the guest when appropriate battery ports are read/written to.
  */
 
+#define _GNU_SOURCE         /* for asprintf() */
 #include <stdio.h>
 #include <stdarg.h>
 #include <string.h>
@@ -101,7 +102,7 @@ FILE *get_next_battery_file(DIR *battery_dir,
 {
     FILE *file = 0;
     struct dirent *dir_entries;
-    char file_name[284];
+    char *file_name;
     int ret;
     
     do 
@@ -112,16 +113,16 @@ FILE *get_next_battery_file(DIR *battery_dir,
         if ( strlen(dir_entries->d_name) < 4 )
             continue;
         if ( battery_info_type == BIF ) 
-            ret = snprintf(file_name, sizeof(file_name), BATTERY_INFO_FILE_PATH,
+            ret = asprintf(&file_name, BATTERY_INFO_FILE_PATH,
                      dir_entries->d_name);
         else 
-            ret = snprintf(file_name, sizeof(file_name), BATTERY_STATE_FILE_PATH,
+            ret = asprintf(&file_name, BATTERY_STATE_FILE_PATH,
                      dir_entries->d_name);
         /* This should not happen but is needed to pass gcc checks */
         if (ret < 0)
             continue;
-        file_name[sizeof(file_name) - 1] = '\0';
         file = fopen(file_name, "r");
+	free(file_name);
     } while ( !file );
 
     return file;