使用std :: copy进行分段错误,memcpy有效

Question

我有一个奇怪的情况,使用std :: copy导致seg故障,因为使用memcpy似乎正常工作.

我正在PacketHeaderGoogle Test函数中创建一个对象.

我已经确认进入对象的数据是有效的,所以我可能是愚蠢的,并且错过了std :: copy语法的明显内容.

GCC版本:4.4.6 20120305(Red Hat 4.4.6-4)GTest版本:1.6.0

还与boost :: options和libpcap链接

TEST(SetIP, GoodVals)
{


    char errbuf[PCAP_ERRBUF_SIZE];
    pcap_t * handle = pcap_open_offline("./test_files/PCAP_Good.pcap", errbuf);

    pcap_pkthdr * header;
    const unsigned char * pkt_data;

    //Load one packet from the PCAP, doesn't matter what
    pcap_next_ex(handle, &header, &pkt_data);

    PacketHeader p(header);

}


PacketHeader::PacketHeader(const struct pcap_pkthdr * aPacketHeader) : prPacketHeader(NULL)
{
    prPacketHeader = new struct pcap_pkthdr;

    //This doesn't work
    //std::copy(aPacketHeader, aPacketHeader + sizeof(struct pcap_pkthdr), prPacketHeader);

    //This works
    memcpy(prPacketHeader, aPacketHeader, sizeof(struct pcap_pkthdr));

}

Answer 1

表达方式

aPacketHeader + sizeof(struct pcap_pkthdr)

不符合你的期望.它实际上添加sizeof(pcap_pkthdr) * sizeof(pcap_pkthdr)到指针基地址.

请记住,这aPointer + something是一样的aPointer[something].

要么只添加1:

aPacketHeader + 1

或类型转换为char*:

reinterpret_cast<char*>(aPacketHeader) + sizeof(struct pcap_pkthdr)

显而易见的解决方案当然应该使用简单的struct-to-struct复制:

*prPacketHeader = *aPacketHeader;