一直以来的印象是匿名联合体兼容性不是很好。今天看代码似乎各个编译器都有做兼容，差不多也是事实性标配了。或许以后可以放心大胆的使用。
typedef struct A {
union {
uint8_t *p8;
uint16_t *p16;
uint32_t *p32;
}
};
/* ------- Start of section using anonymous unions and disabling warnings ------- */
#if defined (__CC_ARM)
#pragma push
#pragma anon_unions
#elif defined (__ICCARM__)
#pragma language=extended
#elif defined(__ARMCC_VERSION) && (__ARMCC_VERSION >= 6010050)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wc11-extensions"
#pragma clang diagnostic ignored "-Wreserved-id-macro"
#elif defined (__GNUC__)
/* anonymous unions are enabled by default */
#elif defined (__TMS470__)
/* anonymous unions are enabled by default */
#elif defined (__TASKING__)
#pragma warning 586
#elif defined (__CSMC__)
/* anonymous unions are enabled by default */
#else
#warning Not supported compiler type
#endif
...
...
/* -------- End of section using anonymous unions and disabling warnings -------- */
#if defined (__CC_ARM)
#pragma pop
#elif defined (__ICCARM__)
/* leave anonymous unions enabled */
#elif (defined(__ARMCC_VERSION) && (__ARMCC_VERSION >= 6010050))
#pragma clang diagnostic pop
#elif defined (__GNUC__)
/* anonymous unions are enabled by default */
#elif defined (__TMS470__)
/* anonymous unions are enabled by default */
#elif defined (__TASKING__)
#pragma warning restore
#elif defined (__CSMC__)
/* anonymous unions are enabled by default */
#else
#warning Not supported compiler type
#endif
参考自文件。