[英]try/catch with __debugbreak()
I am working with a 3rd party C++ DLL that is running __debugbreak() in some scenario, and is not checking IsDebuggerPresent() before doing so. 我正在使用在某些情况下正在运行__debugbreak()的第三方C ++ DLL,并且在这样做之前未检查IsDebuggerPresent()。 This results in my application "crashing" when that scenario happens outside of a debugger (eg end user running the application).
当这种情况发生在调试器之外时(例如,运行该应用程序的最终用户),这导致我的应用程序“崩溃”。 I would like to catch this and deal with it myself, or at least ignore it.
我想自己抓住它,或者至少忽略它。
I actually have had an unhandled exception filter in place to translate SEH to C++ exceptions for a while, so it's a little strange that it's not working. 实际上,我有一个未处理的异常过滤器,可以将SEH转换为C ++异常一段时间,所以它不起作用有点奇怪。
::SetUnhandledExceptionFilter(OnUnhandledException);
I've been doing some direct testing, and the standard __try/__except works, so I could wrap every call into the DLL with this as a fallback, but seems to be that if __try/__except works, then ::SetUnhandledExceptionFilter() should also work. 我一直在进行一些直接测试,并且标准的__try / __ except可以工作,因此我可以将每次调用都包装到DLL中,以作为备用,但似乎是如果__try / __ except可以工作,则:: SetUnhandledExceptionFilter()应该可以也可以。
__try
{
__debugbreak();
}
__except (EXCEPTION_EXECUTE_HANDLER)
{
printf("caught");
}
try/catch(...) does not work. try / catch(...)不起作用。
try
{
__debugbreak();
}
catch (...)
{
printf("caught");
}
_set_se_translator() isn't working either. _set_se_translator()也不起作用。
From the MSDN documentation at https://msdn.microsoft.com/en-us/library/ms679297(VS.85).aspx it states that it should function as a structured exception. 从https://msdn.microsoft.com/zh-cn/library/ms679297(VS.85).aspx上的MSDN文档中,它声明它应作为结构化异常起作用。 I realize that is the documentation for DebugBreak() but I have tested with that as well and have the same problem, even with "catch(...)".
我意识到这是DebugBreak()的文档,但是我也对此进行了测试,即使遇到“ catch(...)”,也存在相同的问题。
I am compiling with /EHa. 我正在使用/ EHa进行编译。
How can I catch the __debugbreak (asm INT 3), or at least change the behavior? 如何捕获__debugbreak(asm INT 3),或者至少更改行为?
Breakpoints generate the EXCEPTION_BREAKPOINT
structured exception. 断点生成
EXCEPTION_BREAKPOINT
结构化异常。 You cannot use try/catch to catch it because it doesn't get translated to a C++ exception, irrespective of the /EHa switch or _set_se_translator
. 您不能使用try / catch来捕获它,因为无论/ EHa开关还是
_set_se_translator
,它都不会转换为C ++异常。 EXCEPTION_BREAKPOINT
is a special exception. EXCEPTION_BREAKPOINT
是一个特殊的例外。
First, you should know that catch blocks and __except blocks execute only after unwinding the stack. 首先,您应该知道catch块和__except块仅在展开堆栈后才执行。 This means that execution continues after the handler block, NOT after the call to
__debugbreak()
. 这意味着执行将在处理程序块之后继续执行,而不是在调用
__debugbreak()
之后继续执行。 So if you just want to skip EXCEPTION_BREAKPOINT
while at the same time continue execution after the int 3
instruction. 因此,如果您只想跳过
EXCEPTION_BREAKPOINT
而同时在int 3
指令之后继续执行。 You should use a vectored exception handler. 您应该使用向量异常处理程序。 Here is an example:
这是一个例子:
// VEH is supported only on Windows XP+ and Windows Server 2003+
#define _WIN32_WINNT 0x05020000
#include <windows.h>
#include <stdio.h>
//AddVectoredExceptionHandler constants:
//CALL_FIRST means call this exception handler first;
//CALL_LAST means call this exception handler last
#define CALL_FIRST 1
#define CALL_LAST 0
LONG WINAPI
VectoredHandlerBreakPoint(
struct _EXCEPTION_POINTERS *ExceptionInfo
)
{
if (ExceptionInfo->ExceptionRecord->ExceptionCode == EXCEPTION_BREAKPOINT)
{
/*
If a debugger is attached, this will never be executed.
*/
printf("BreakPoint at 0x%x skipped.\n", ExceptionInfo->ExceptionRecord->ExceptionAddress);
PCONTEXT Context = ExceptionInfo->ContextRecord;
// The breakpoint instruction is 0xCC (int 3), just one byte in size.
// Advance to the next instruction. Otherwise, this handler will just be called ad infinitum.
#ifdef _AMD64_
Context->Rip++;
#else
Context->Eip++;
#endif
// Continue execution from the instruction at Context->Rip/Eip.
return EXCEPTION_CONTINUE_EXECUTION;
}
// IT's not a break intruction. Continue searching for an exception handler.
return EXCEPTION_CONTINUE_SEARCH;
}
void main()
{
// Register the vectored exception handler once.
PVOID hVeh = AddVectoredExceptionHandler(CALL_FIRST, VectoredHandlerBreakPoint);
if (!hVeh)
{
// AddVectoredExceptionHandler failed.
// Practically, this never happens.
}
DebugBreak();
// Unregister the handler.
if (hVeh)
RemoveVectoredExceptionHandler(hVeh);
}
In this way, the breakpoint instruction int 3
will just be skipped and the next instruction will be executed. 这样,断点指令
int 3
将被跳过,而下一条指令将被执行。 Also if a debugger is attached, it will handle EXCEPTION_BREAKPOINT
for you. 另外,如果连接了调试器,它将为您处理
EXCEPTION_BREAKPOINT
。
However, if you really want to unwind the stack, you have to use __except(GetExceptionCode() == EXCEPTION_BREAKPOINT ? EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH)
. 但是,如果您真的想展开堆栈,则必须使用
__except(GetExceptionCode() == EXCEPTION_BREAKPOINT ? EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH)
。
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