Question

我在一些安全关键汽车模块中运行了代码。以下是对代码的粗略估计：

以下代码是模块的一部分 - ＆＃34;主要模块＆＃34; ，拥有volatile变量/数组＆＃34; x_ast＆＃34;

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.

以下代码是模块的一部分 - ＆＃34; DependentModule＆＃34;这样可以共享缓冲区＆＃34; x_ast＆＃34;。

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];

以上代码行（Tempptr =（x_tst *）＆amp; x_ast [1];）会发出警告＆＃34; 消息（7：0312）危险指针投射结果失去资格。＆＃34; 上述警告是强制性警告，因此有必要解决它。

我明白我正在为void指针分配一个volatile变量的地址，导致挥发性资格的丢失。我尝试过尝试解决警告的不同方法，但无法得出确定的方法。

有什么办法，我可以修改代码并删除此警告，或者可以绕过此警告。

Answer 1

如果为volatile对象赋值或在不使用volatile限定指针的情况下读取volatile对象的值，则会得到未定义的行为。

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视为易失性就好了，将易失性对象视为非易失性对象可能有坏处理后果）。

将易失性对象的地址强制转换为非易失性指针会使您面临极大的风险。不要做。使用该void *指针的人很有可能调用未定义的行为。例如，仅使用memcpy复制易失性数组是未定义的行为。任何事情，通常是坏事，都可能发生。

将该函数声明为

boolean GetConditionalBuffer(volatile x_tst **PtrToBuffer)

因为volatile x_tst *是它存储在PtrToBuffer中的内容。你为什么要扔掉类型信息？我实际上将其改为

volatile x_tst* GetConditionalBuffer (void);

这使得开发人员的大脑变得更容易，并使该功能更易于使用。

失去资格的挥发性

1 个答案: