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Subject: Re: [boost] [Stacktrace] review, please stop discussing non-Stacktrace issues
From: Peter Dimov (lists_at_[hidden])
Date: 2016-12-17 13:32:48

Niall Douglas wrote:

> In an exception handler you cannot call any async unsafe routine such as
> anything in MSVCRT nor anything
implemented by kernel32.dll in userspace. As on POSIX, almost all syscalls
implemented entirely in kernel space are safe.

Thanks Niall. Do you know which Windows API functions are safe and which
aren't? I couldn't find a list anywhere.

> Antony makes the valid point that on Windows there are race problems with
> the DbgHelp library, in fact not only is it not async-unsafe, it's also
> thread-unsafe.

He doesn't use DbgHelp in the Windows backend though, he uses Dbgeng.h. This
is not the same thing, I think?

> Of course Windows has signals, as already referred to by myself earlier
> it's called vectored exception handling which is exactly the same as a
> signal implementation.

Not quite. A signal immediately suspends the thread and calls the handler in
it. Windows exception handling, in contrast, unwinds the stack. So if the
kernel crashes somewhere deep, it can unwind itself to a usable state before
the program gets to handle the exception. Or at least that's my

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