Compiling current master with the ultimate gcc 6 (6.2.1 in my case) brings this warning. While technically useless it can hide important stuff.
CXX wallet/libbitcoin_wallet_a-rpcdump.o
wallet/rpcdump.cpp: In function 'UniValue importmulti(const JSONRPCRequest&)':
wallet/rpcdump.cpp:1020:13: warning: 'nLowestTimestamp' may be used uninitialized in this function [-Wmaybe-uninitialized]
int64_t nLowestTimestamp;
^~~~~~~~~~~~~~~~