From: Andy Green Date: Tue, 22 May 2018 01:24:32 +0000 (+0800) Subject: mbuf: avoid implicit demotion in 64-bit arithmetic X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=ef5092e16b137fd5e23d19b4b17b32f330d4a4ad;p=dpdk.git mbuf: avoid implicit demotion in 64-bit arithmetic GCC 8.1 warned: In function 'rte_validate_tx_offload': rte_mbuf.h:2112:19: warning: conversion to 'uint64_t' {aka 'long unsigned int'} from 'int' may change the sign of the result [-Wsign-conversion] inner_l3_offset += m->outer_l2_len + m->outer_l3_len; ^~ uint64_t inner_l3_offset... /* fields for TX offloading of tunnels */ uint64_t outer_l3_len:9; /**< Outer L3 (IP) Hdr Length. */ uint64_t outer_l2_len:7; /**< Outer L2 (MAC) Hdr Length. */ We want to do the arithmetic entirely in uint64_t space, but with the +=, the rhs type becomes int since the bitfields will fit in int. Elaborate the artithmetic to be u64 = u64 + int + int, so the type of the result is correct to be stored in the u64. Fixes: 4fb7e803eb ("ethdev: add Tx preparation") Cc: stable@dpdk.org Signed-off-by: Andy Green Acked-by: Bruce Richardson --- diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h index 715f90ea03..0e89a69270 100644 --- a/lib/librte_mbuf/rte_mbuf.h +++ b/lib/librte_mbuf/rte_mbuf.h @@ -2112,7 +2112,11 @@ rte_validate_tx_offload(const struct rte_mbuf *m) return 0; if (ol_flags & PKT_TX_OUTER_IP_CKSUM) - inner_l3_offset += m->outer_l2_len + m->outer_l3_len; + /* NB: elaborating the addition like this instead of using + * += gives the result uint64_t type instead of int, + * avoiding compiler warnings on gcc 8.1 at least */ + inner_l3_offset = inner_l3_offset + m->outer_l2_len + + m->outer_l3_len; /* Headers are fragmented */ if (rte_pktmbuf_data_len(m) < inner_l3_offset + m->l3_len + m->l4_len)