丢失挥发性限定

Question

我在一些安全关键汽车模块中运行代码。下面是代码的一个粗略估计：

在下面的代码是一个模块的一部分 - “主模块”，拥有该易失性可变/数组“x_ast”

Main Module.c 

//The structure x contains the major data that needs to be stored in case of a crash event. i.e. a real car crash 
// x contains data such a vehicle speed, environment data, sensor data, CAN related data,etc. Basically x itself has lot of structures inside it. 


typedef struct x x_tst; 
volatile x_tst x_ast[5]; 
//x_ast is being used in realtime and background functions, considering proper interrupt disabling and enabling. 

在下面的代码是模块的一部分 - “DependentModule”，可以共享缓冲区“x_ast”。

DependentModule.c 

extern volatile x_tst x_ast[5]; 


//x_ast is owned by a separate module 
//Now I need to share this buffer "x_ast" to a different module that will inturn fill data in it for some conditions. Say for a particular condition that is activated, the buffer "x_ast" will be shared across to a module "Conditional Data Record". 
//The base address of first indexed buffer "x_ast[1]" is provided to "Conditional Data Record" for access. 
//The main module will not access the buffer that is shared, once the "Conditional Data Record" is activated/requested. 

// Below is a mechanism to share the buffer "x_ast" to module "Conditional Data Record". 

// This API will be called by module - "Conditional Data Record" once it is activated. It is ensured that this takes place only during intialization of whole system, and no other time. 

boolean GetConditionalBuffer(uint8 **PtrToBuffer) 
{ 
    boolean BufferShared = FALSE; 
    void* Temp_ptr; 
    *PtrToBuffer = NULL; 

// if module "Conditional Data Record" is activated? then share the buffer "x_ast", else do not share the buffer. 

if(Conditional Data Record == activated) { 
    Temp_ptr = (x_tst*)&x_ast[1]; 
    *PtrToBuffer = Temp_ptr; 
    BufferShared = TRUE; 
} 

return BufferShared; 

} 



Referring to the line of code: 
Temp_ptr = (x_tst*)&x_ast[1]; 

的代码（Tempptr =（x_tst *）& x_ast [1]）的上面的行抛出一个警告“消息（7：0312）。危险指针铸造导致挥发性资格的损失 “ 上述警告是强制性警告，因此有必要解决它。

我知道我将一个volatile变量的地址赋值给一个void指针，导致volatile限定的丢失。 我尝试了不同的方法试图解决警告，但无法得到确凿的方法。

有没有什么办法，我可以修改代码并删除这个警告，或者可以绕过这个警告。

Answer 1

如果您将值分配给易失性对象或在不使用易失性限定指针的情况下读取易失性对象的值，则会出现未定义的行为。

编译器必须以比非易失性对象更严格的方式处理易失性对象（这意味着将非易失性对象当作易失性对象处理很好，将易失性对象视为非易失性对象可以有坏的后果）。

将易失性对象的地址投射到非易失性指针是使您面临严重风险。不要这样做。无论谁使用void *指针都会引发未定义的行为。例如，仅使用memcpy复制该易失性数组是未定义的行为。任何事情，通常都是坏事，都可能发生。

声明一个功能

boolean GetConditionalBuffer(volatile x_tst **PtrToBuffer) 

因为挥发性x_tst *是它存储到PtrToBuffer。为什么你会丢弃类型信息？我实际上将其更改为

volatile x_tst* GetConditionalBuffer (void); 

这使得它更容易开发人员的大脑，使功能更容易使用。