遭遇bus error

以前在6467上似乎没遇到这个问题，最近在DM368(arm_v5t_le-)上遇到了

传说是因为编译优化选项引起的(-O2),可去掉测试看下

此外的解决方法是使用临时变量及memcpy

两个代码片段

static int replaceVideostartCode(char* data, int len, int isKey)
{
    int i = 0;
    unsigned int startCode = 0;
    int lastStartCodepos = 0;
    int tofoundtimes = 2;
    int alreadyfound = 0;

    if(!data || len < 4)
    {
        return 0;
    }

    if(((data[i] << 24) | (data[i+1] << 16) |(data[i+2] << 8) | data[i+3]) != 0x00000001)
    {
        return 0;
    }

    if(isKey)
    {
        tofoundtimes = 4;/* sps pps sei iSlice */
    }

    for(i = 0;i < len - 3 && alreadyfound < tofoundtimes;i++)
    {
        startCode = (data[i] << 24) | (data[i+1] << 16) |(data[i+2] << 8) | data[i+3];
        if(startCode == 0x00000001)
        {
            if(i > 0)
            {
                *((unsigned int*)(data + lastStartCodepos)) = htonl(i - lastStartCodepos - 4);
            }
            lastStartCodepos = i;
            alreadyfound++;
        }
    }

    *((unsigned int*)(data + lastStartCodepos)) = htonl(len - lastStartCodepos - 4);
    return 1;
}


static int replaceVideostartCode2(char* data, int len, int isKey)
{
    int i = 0;
    unsigned int startCode = 0;
    int lastStartCodepos = 0;
    int tofoundtimes = 2;
    int alreadyfound = 0;
    unsigned char tmp0 = 0;
    unsigned char tmp1 = 0;
    unsigned char tmp2 = 0;
    unsigned char tmp3 = 0;
    unsigned int  tmp = NULL;

    if(!data || len < 4)
    {
        return 0;
    }

    tmp0 = data[0];
    tmp1 = data[1];
    tmp2 = data[2];
    tmp3 = data[3];
    if(((tmp0 << 24) | (tmp1 << 16) | (tmp2 << 8) | tmp3) != 0x00000001)
    {
        printf("replaceVideostartCode out \n");
        return 0;
    }

    if(isKey)
    {
        tofoundtimes = 4;
    }

    for(i = 0;i < len - 3 && alreadyfound < tofoundtimes;i++)
    {
        tmp0 = data[i + 0];
        tmp1 = data[i + 1];
        tmp2 = data[i + 2];
        tmp3 = data[i + 3];
        startCode = (tmp0 << 24) | (tmp1 << 16) | (tmp2 << 8) | tmp3;
        if(startCode == 0x00000001)
        {
            if(i > 0)
            {
                tmp = htonl(i - lastStartCodepos - 4);
                memcpy(data + lastStartCodepos, (unsigned char*)&tmp, sizeof(unsigned int));
            }
            lastStartCodepos = i;
            alreadyfound++;
        }
    }

    tmp = htonl(len - lastStartCodepos - 4);
    memcpy(data + lastStartCodepos, (unsigned char*)&tmp, sizeof(unsigned int));
    return 1;
}

#if 1
    tmp = htons(pos[1].len);
    memcpy(towrite + 1, (unsigned char*)&tmp, sizeof(unsigned short));
    towrite += sizeof(unsigned short) + 1;
#else
    towrite += 1;
    *((unsigned short*)(towrite)) = htons(pos[1].len);
    towrite += sizeof(unsigned short);
#endif