get_rev_contents() has signed integer overflow with "long int" rev
and behaves unpredictably.

--- subversion-1.12.2/subversion/tests/libsvn_fs_fs/fs-fs-pack-test.c.fsfspacktest
+++ subversion-1.12.2/subversion/tests/libsvn_fs_fs/fs-fs-pack-test.c
@@ -59,7 +59,8 @@
 get_rev_contents(svn_revnum_t rev, apr_pool_t *pool)
 {
   /* Toss in a bunch of magic numbers for spice. */
-  apr_int64_t num = ((rev * 1234353 + 4358) * 4583 + ((rev % 4) << 1)) / 42;
+  apr_int64_t rev64 = rev;
+  apr_int64_t num = ((rev64 * 1234353 + 4358) * 4583 + ((rev64 % 4) << 1)) / 42;
   return apr_psprintf(pool, "%" APR_INT64_T_FMT "\n", num);
 }
 
@@ -407,7 +408,8 @@
 
       if (! svn_stringbuf_compare(rstring, sb))
         return svn_error_createf(SVN_ERR_FS_GENERAL, NULL,
-                                 "Bad data in revision %ld.", i);
+                                 "Bad data in revision %ld - [%s] not [%s].",
+                                 i, rstring->data, sb->data);
     }
 
   return SVN_NO_ERROR;