Use HAVE_STRUCT_STAT_ST_BLOCKS, not deprecated HAVE_ST_BLOCKS.

[gnulib.git] / lib / canon-host.c

diff --git a/lib/canon-host.c b/lib/canon-host.c
index db19538..0c7eac4 100644 (file)
--- a/lib/canon-host.c
+++ b/lib/canon-host.c
@@ -43,6 +43,8 @@
 # include <arpa/inet.h>
 #endif
 
+void free ();
+
 /* Returns the canonical hostname associated with HOST (allocated in a static
    buffer), or 0 if it can't be determined.  */
 char *
@@ -67,9 +69,23 @@ canon_host (const char *host)
        }
 
       if (addr && strcmp (he->h_name, addr) == 0)
-       /* gethostbyname() cheated!  Lookup the host name via the address
-          this time to get the actual host name.  */
-       he = gethostbyaddr (he->h_addr, he->h_length, he->h_addrtype);
+       {
+         /* gethostbyname has returned a string representation of the IP
+            address, for example, "127.0.0.1".  So now, look up the host
+            name via the address.  Although it may seem reasonable to look
+            up the host name via the address, we must not pass `he->h_addr'
+            directly to gethostbyaddr because on some systems he->h_addr
+            is located in a static library buffer that is reused in the
+            gethostbyaddr call.  Make a copy and use that instead.  */
+         char *h_addr_copy = strdup (he->h_addr);
+         if (h_addr_copy == NULL)
+           he = NULL;
+         else
+           {
+             he = gethostbyaddr (h_addr_copy, he->h_length, he->h_addrtype);
+             free (h_addr_copy);
+           }
+       }
 # endif /* HAVE_GETHOSTBYADDR */
 
       if (he)
@@ -78,3 +94,17 @@ canon_host (const char *host)
 #endif /* HAVE_GETHOSTBYNAME */
   return 0;
 }
+
+#ifdef TEST_CANON_HOST
+int
+main (int argc, char **argv)
+{
+  int i;
+  for (i = 1; i < argc; i++)
+    {
+      char *s = canon_host (argv[i]);
+      printf ("%s: %s\n", argv[i], (s ? s : "<undef>"));
+    }
+  exit (0);
+}
+#endif /* TEST_CANON_HOST */