Re: signals on windows

[Marsh Ray <marsh-pg(at)mysteray(dot)com>]

Hi,
This MS documentation looks like it's slightly retro. I've been trying 
to decypher this stuff myself for a decade, so I might offer some points:.

> Andrew Dunstan wrote:
>  
>
> > *   Note   SIGINT is not supported for any Win32 application, including
> > *   Windows 98/Me and Windows NT/2000/XP.When a CTRL+C interrupt occurs,
> > *   Win32 operating systems generate a new thread to specifically handle
> > *   that interrupt. This can cause a single-thread application such as 
> > UNIX,
> > *   to become multithreaded, resulting in unexpected behavior.
Odd. First they say it's not supported, then they go on to define how it 
works. Probably what they mean is that Win32 _GUI_ applications have no 
way to have receive SIGINT from Ctrl+C, because that's handled as just 
another keystroke by the GUI system (sometimes you'll see the older 
documentation use Win32 as a term implying GUI).  Win32 console apps 
appear to respond to Ctrl+C much like unices do.

Since Win32 will create a new thread for you, if you prepare your app 
for that, I don't see a reason you can't make pure Win32 system calls 
from that thread. You mainly want to be careful to not confuse a 
single-threaded C runtime. Note that the doc 
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclib/html/_CRT_signal.asp 
says not to "use any function that generates a system call (e.g., 
*_getcwd*, *time*)", it doesn't say not to make system calls themselves. 
It doesn't look like a "signal" is not a kernel primitive on NT, it's a 
feature of the CRT implemented in userspace with lower-level OS primitives.

> > * I have no idea how to handle this. (Strange they call UNIX an 
> > application!)
> > * So this will need some testing on Windows.
> > * One alternative might be to set a flag that we periodically check for.
A kernel Event 
(http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/base/createevent.asp) 
is a common tool for this sort of thing.

- Marsh