嵌套的 __try...__except 子句,这是如何工作的?

Nested __try...__except clauses, how does this work?

我正在处理一个函数和一个子函数,子函数在函数内被调用。两者都有一个 __try .. __except 子句,我想看看函数的一般异常处理,以及子函数的具体异常处理,换句话说:

int function(){
__try{
  do_something();
  return subfunction();
  } __except (Exception_Execute_Handler_Something()){
  show("general exception");
  }

int subfunction(){
  __try{
    return do_something_else();
  } __except (Exception_Execute_Handler_Something_Else()){
    show("specific case");
  }

在这种情况下:
do_something() 出错时,我看到 "general exception".
do_something_else()出错的时候,我也看到了"general exception",这不是我想要的

我要的是:
do_something()出错时,我想看到“一般异常。
do_something_else()出问题的时候,想看"specific case".

根据 Ben Voight 的评论进行编辑

确实有一个异常过滤器,目前正在检查异常代码以决定是否继续,如您所见:

if (Exception->ExceptionCode == STATUS_ACCESS_VIOLATION)
  return EXCEPTION_CONTINUE_SEARCH;

然而,我对异常处理的两个输入参数ExceptionRecordContextRecord的结构and/or内容一无所知。在此,我举例说明这些参数在我的特定情况下是什么样的:

异常记录:

-   ExceptionRecord 0x0eecdec8 {ExceptionCode=3221225620 ExceptionFlags=0 ExceptionRecord=0x00000000 <NULL> ...}    _EXCEPTION_RECORD *
    ExceptionCode   3221225620  unsigned long // I guess this means division by zero
    ExceptionFlags  0   unsigned long
+   ExceptionRecord 0x00000000 <NULL>   _EXCEPTION_RECORD *
    ExceptionAddress    0x002c1993 {<Application>.exe!CClass::Main_Method(CInputClass & params), Line 46}   void *
    NumberParameters    0   unsigned long
+   ExceptionInformation    0x0eecdedc {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}    unsigned long[15]

上下文记录:

-   ContextRecord   0x0eecdf18 {ContextFlags=65543 Dr0=0 Dr1=0 ...} _CONTEXT *
    ContextFlags    65543   unsigned long
    Dr0 0   unsigned long
    Dr1 0   unsigned long
    Dr2 0   unsigned long
    Dr3 0   unsigned long
    Dr6 0   unsigned long
    Dr7 0   unsigned long
-   FloatSave   {ControlWord=0 StatusWord=0 TagWord=0 ...}  _FLOATING_SAVE_AREA
    ControlWord 0   unsigned long
    StatusWord  0   unsigned long
    TagWord 0   unsigned long
    ErrorOffset 0   unsigned long
    ErrorSelector   0   unsigned long
    DataOffset  0   unsigned long
    DataSelector    0   unsigned long
+   RegisterArea    0x0eecdf50 ""   unsigned char[80] // all are zero
    Spare0  0   unsigned long
    SegGs   43  unsigned long
    SegFs   83  unsigned long
    SegEs   43  unsigned long
    SegDs   43  unsigned long
    Edi 80923496    unsigned long
    Esi 250405956   unsigned long
    Ebx 0   unsigned long
    Edx 0   unsigned long
    Ecx 0   unsigned long
    Eax 1   unsigned long
    Ebp 250405884   unsigned long
    Eip 2890131 unsigned long
    SegCs   35  unsigned long
    EFlags  66118   unsigned long
    Esp 250405880   unsigned long
    SegSs   43  unsigned long
+   ExtendedRegisters   0x0eecdfe4 "\x2 \x1"    unsigned char[512] // at first sight, not readable

现在我的问题变成了:

如果我已经在另一个 __try..__except 子句中,我会 return EXCEPTION_CONTINUE_SEARCH.

有谁知道我可以使用所提到的 ExceptionRecordContextRecord 属性中的哪一个来确定我是否已经在另一个 __try..__except 子句中?

再补充一些信息后重新编辑

我刚刚找到 EXCEPTION_DISPOSITION,出现在 C:\Program Files (x86)\Microsoft Visual Studio17\Professional\VC\Tools\MSVC.16.27023\include\excpt.h 中。这包含函数 _except_handler(),其中 returns 是一个 EXCEPTION_DISPOSITION 枚举,它可以是 ExceptionNestedException(我相信这就是我要找的那个)。
所以现在问题变成了:

What parameters do I need to fill in in the function _except_handler() in order to know if I'm dealing with a nested exception (or does somebody know an easier way to get this done)?

您编写的代码无法编译。而不是:

__except { ... }

你需要:

__except (EXCEPTION_EXECUTE_HANDLER) { ... }

然后它就如愿以偿了。

Live demo

#include <iostream>
#include <Windows.h>

int do_something_else()
{
    *(reinterpret_cast<int*>(0)) = 1;
    return 0;
}

int do_something()
{
    return 0;
}

int subfunction();

int32_t ReportCrash(LPEXCEPTION_POINTERS ExceptionInfo) //exception and context pointers are hrere
{
    return EXCEPTION_EXECUTE_HANDLER;
}

int function()
{
    __try 
    {
        do_something();
        return subfunction();
    }
    __except (ReportCrash(GetExceptionInformation()))
    {
        std::cout << ("general exception");
    }
    return 0;
}

int subfunction()
{
    __try 
    {
        return do_something_else();
    }
    __except (ReportCrash(GetExceptionInformation()))
    {
        std::cout << ("specific case");
    }
    return 0;
}

int main()
{
    std::cout << "Hello World!\n"; 

    function();
}

详情为here

你可以使用 RaiseException。

#define SUBCODE 0x1000

int Filter(LPEXCEPTION_POINTERS exceptionPointers,DWORD& code) {
  code = exceptionPointers->ExceptionRecord->ExceptionCode;
  return EXCEPTION_EXECUTE_HANDLER;
}

int function(){
  DWORD code;
  __try{
      do_something();
      return subfunction();
    } __except ( Filter( GetExceptionInformation(), code )  ){  
      if (code == SUBCODE) {
        show("specific case");      
      } else {
        show("generic code");
      }
    }
}

int subfunction(){
  __try{
    return do_something_else();
  } __except (EXCEPTION_EXECUTE_HANDLER){
    RaiseException( SUBCODE , 0, 0 , NULL );
  }
}

EXCEPTION_RECORD 结构有一个名为 ExceptionRecord 的成员,它是指向另一个 EXCEPTION_RECORD 的指针...这就是您判断是否有嵌套异常的方式。