C中的双重功能间接 [英] Double function indirection in C

问题描述

我正在为ARM Cortex-M0 CPU编写引导加载程序.我需要将IRQ转发到目标应用程序，不幸的是，此CPU中的IRQ向量位于固定地址，并且无法重定位它，因此我需要一些技巧.

I am writing a bootloader for an ARM Cortex-M0 CPU. I need to forward the IRQs to the target app, unfortunately the IRQ vector in this CPU is at fixed address and I cannot relocate it, so I need a bit of trickery.

我知道目标应用程序的IRQ地址的存储地址. 这么说吧，在地址0x5008处是void x_IRQHandler(void)(目标应用)的地址

I know the address where the addresses of the target app's IRQs are stored. So let's say, at address 0x5008 there's the address of void x_IRQHandler(void) (target app)

我想做的是:

• 在启动时保存所有x_IRQHandler()的地址(这样就不会在运行时对其进行计算)；
• 只要引导加载程序收到IRQ调用，就从目标应用程序的地址中调用相关的IRQ函数.

这是我在引导程序中所做的，我找不到正确的语法.

This is what I have done in the bootloader, I can't find the right syntax for it.

//pointers to x_IRQHandler() functions
void(* x_IRQ_addr)(void);
x_IRQ_addr = (void(*)(void))(0x5008);

//here I should call the function pointed by x_IRQ_addr; but this syntax is not valid
void x_IRQ_Handler(void)
{
  *x_IRQ_addr();
}

我尝试了不同的方法但均未成功，该如何解决?

I have tried different approaches with no success, how can I fix that?

推荐答案

函数调用运算符()的优先级高于间接运算符*.

The function call operator () has higher precedence than the indirection operator *.

尝试使用(*x_IRQ_addr)();而不是*x_IRQ_addr();.

您也可以将其写为x_IRQ_addr();，因为*x_IRQ_addr是函数指定符，它将被转换为指向()运算符的操作数的函数的指针，因此取消引用就浪费了.

You can also write it as x_IRQ_addr(); because *x_IRQ_addr is a function designator and it will be converted to the pointer pointing the function for operand of () operator, so the dereference goes to waste.

这篇关于C中的双重功能间接的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！