buffer overflow in libctf tests

* testsuite/libctf-regression/gzrewrite.c (main): Don't overflow
       "a" buffer in "after adding types" check.
       * testsuite/libctf-regression/zrewrite.c (main): Likewise.

libctf/testsuite/libctf-regression/gzrewrite.c

@@ -114,7 +114,7 @@ main (int argc, char *argv[])
   if ((b = read_gz ("tmpdir/two.gz", &b_len)) == NULL)
     goto read_err;
 
-  if (memcmp (a, b, b_len) == 0)
+  if (a_len == b_len && memcmp (a, b, b_len) == 0)
     {
       fprintf (stderr, "gzwrites after adding types does not change the dict\n");
       return 1;

libctf/testsuite/libctf-regression/zrewrite.c

@@ -109,7 +109,7 @@ main (int argc, char *argv[])
 
   b = read_file ("tmpdir/two", &b_len);
 
-  if (memcmp (a, b, b_len) == 0)
+  if (a_len == b_len && memcmp (a, b, b_len) == 0)
     {
       fprintf (stderr, "compress_writes after adding types does not change the dict\n");
       return 1;