GCC代码移植到Keil遇到的问题

需要从GCC下的代码移植到Keil下，发现对齐这边编译无法通过，原来他们是不兼容的，需要做些修改：

<span style="font-size:14px;">//Keil下 
typedef __packed union { 
  uint16_t W; 
  __packed struct { 
    uint8_t L; 
    uint8_t H; 
  } WB; 
} WORD_BYTE; 


//GCC下 
struct _WB{ 
    uint8_t L; 
    uint8_t H; 
}__attribute__ ((packed)); 


typedef union _WORD_BYTE WORD_BYTE; 
union _WORD_BYTE{ 
    uint16_t W; 
    struct _WB WB; 
}__attribute__ ((packed)); </span>

GCC不支持左值强制类型运算(这点不敢肯定)

<span style="font-size:14px;">//Keil 
(uint8_t *)pD += ((USB_CONFIGURATION_DESCRIPTOR *)pD)->wTotalLength; 

//GCC 
 pD =  ( USB_COMMON_DESCRIPTOR *)((uint8_t *)pD + ((USB_CONFIGURATION_DESCRIPTOR *)pD)->wTotalLength);</span>

GCC无法做对齐强制类型，以下为keil的方式，GCC下做类似动作是不生效的，问题描述里详细介绍

*((__packed uint32_t *)pData) = *((__packed uint32_t *)dataptr);