evrpc_compat - Deprecated versions of the functions in rpc.h: provided
  only for backwards compatibility.
#include <event2/rpc_compat.h>
  
#define EVTAG_LEN(msg, member) ((msg)->member##_length)
backwards compatible accessors that work only with gcc 
Deprecated versions of the functions in rpc.h: provided only for
  backwards compatibility.
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