问题描述
在我的 C++ 程序中，我使用了一个库，它会发送?"特定操作的 Sigtrap 时我正在调试它(使用 gdb 作为调试器).然后我可以选择是要继续还是停止程序.如果我选择继续，程序按预期工作，但在捕获 Sigtrap 后设置自定义断点会导致调试器/程序崩溃.
In my c++ program I'm using a library which will "send?" a Sigtrap on a certain operations when I'm debugging it (using gdb as a debugger). I can then choose whether I wish to Continue or Stop the program. If I choose to continue the program works as expected, but setting custom breakpoints after a Sigtrap has been caught causes the debugger/program to crash.
所以这是我的问题:
- 是什么导致了这种 Sigtrap?它是可以删除的剩余代码行，还是由调试器发现他不喜欢的东西"引起的?
- 一般来说，信号陷阱是一件坏事吗?如果是，为什么当我编译发布版本而不是调试版本时程序可以完美运行?
- Sigtrap 表示什么?
这是我昨天发布的问题的更通用方法 Boost Filesystem:recursive_directory_iterator 构造函数导致 SIGTRAPS 和调试问题.
我认为我的问题很具体，我不希望您解决我的问题，而是帮助我(希望其他人)了解背景.
This is a more general approach to a question I posted yesterday Boost Filesystem: recursive_directory_iterator constructor causes SIGTRAPS and debug problems.
I think my question was far to specific, and I don't want you to solve my problem but help me (and hopefully others) to understand the background.
非常感谢.
推荐答案
对于支持指令断点或数据观察点的处理器，调试器将要求 CPU 观察对特定地址的指令访问，或对特定地址的数据读/写具体地址，然后全速运行.
With processors that support instruction breakpoints or data watchpoints, the debugger will ask the CPU to watch for instruction accesses to a specific address, or data reads/writes to a specific address, and then run full-speed.
当处理器检测到该事件时，它会陷入内核，内核会向被调试的进程发送SIGTRAP.通常，SIGTRAP 会终止进程，但由于它正在被调试，调试器将收到信号通知并处理它，主要是让您在继续执行之前检查进程的状态.
When the processor detects the event, it will trap into the kernel, and the kernel will send SIGTRAP to the process being debugged. Normally, SIGTRAP would kill the process, but because it is being debugged, the debugger will be notified of the signal and handle it, mostly by letting you inspect the state of the process before continuing execution.
对于不支持断点或观察点的处理器，整个调试环境可能是通过代码解释和内存模拟来完成的，这非常慢.(我想巧妙的技巧可以通过设置页表标志来禁止读取或写入，无论哪个需要被捕获，并让内核修复页表，向调试器发出信号，然后再次限制页标志.这可能支持近- 任意数量的观察点和断点，并且在观察点或断点不经常访问的情况下运行速度稍慢.)
With processors that don't support breakpoints or watchpoints, the entire debugging environment is probably done through code interpretation and memory emulation, which is immensely slower. (I imagine clever tricks could be done by setting pagetable flags to forbid reading or writing, whichever needs to be trapped, and letting the kernel fix up the pagetables, signaling the debugger, and then restricting the page flags again. This could probably support near-arbitrary number of watchpoints and breakpoints, and run only marginally slower for cases when the watchpoint or breakpoint aren't frequently accessed.)
我在评论字段中提出的问题在这里看起来很恰当，只是因为 Windows 实际上并没有发送 SIGTRAP，而是以自己的本机方式发出断点信号.我假设当您调试程序时，会使用系统库的调试版本，并确保内存访问看起来是有意义的.您的程序中可能有一个在运行时被掩盖的错误，但实际上可能会在其他地方引起更多问题.
The question I placed into the comment field looks apropos here, only because Windows isn't actually sending a SIGTRAP, but rather signaling a breakpoint in its own native way. I assume when you're debugging programs, that debug versions of system libraries are used, and ensure that memory accesses appear to make sense. You might have a bug in your program that is papered-over at runtime, but may in fact be causing further problems elsewhere.
我还没有在 Windows 上进行过开发，但也许您可以通过查看您的 Windows 事件日志获得更多详细信息?
I haven't done development on Windows, but perhaps you could get further details by looking through your Windows Event Log?
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