c - What is a vuint in C, and why is it in my microcontroller?

Question

I'm flipping through some C header files for a microcontroller, and I keep seeing register addresses initialized as vuint. I haven't come across this data type before, so I did a bit of searching, with no real results. The closest I got was from https://stackoverflow.com/a/12855989, which tells me that v stands for "volatile". So, I have volatile unsigned ints holding hardware register addresses. As in, I have a data type that explicitly states "This address is subject to change", representing registers that are hard-wired, and cannot change, like, ever. Is my understanding of vuint incorrect? If not, why are we representing addresses this way?

Answer 1

内存映射寄存器设置为易失性，因为它们中的值可能由于编译器不知道的外部原因（硬件中断等）而改变。这意味着编译器应避免某些优化并确保实际读取地址（而不是针对缓存值等进行优化）。

快速示例，包含一些标志的内存映射寄存器。

read flags
set bit in flags
interrupt sets another bit
<compiler optimizes and cached flags from before>
read flags <contains incorrect cached value>

Answer 2

我认为您误解了类型。它很可能是指向易失性无符号整数的指针，表明无符号整数是易失性的，而不是指针。这在通过结构描述硬件寄存器时很典型。每个结构成员将是一个易失性无符号整数，并且在某处将定义一个基地址，指示寄存器在内存映射中的起始位置。