RE: Cygwin.dll crash, alloca and custom stack

["Gary R. Van Sickle" <g dot r dot vansickle at worldnet dot att dot net>]

> -----Original Message-----
> From: cygwin-owner@cygwin.com 
> [mailto:cygwin-owner@cygwin.com] On Behalf Of Chris

> Anyway, this similar code does work under Linux, or at least 
> it appears to:
> 

It's a long walk from "at least appears to work" to "does work".

[snip]

> >You just threw away the stack and jumped into space.  What did you 
> >expect to happen?
> 
> While I don't claim to be an uber-expert in assembler, I know 
> I didn't "jump into space".

Yeah dude, you did.  You pulled the rug out from under the C runtime,
Cygwin, and apparently even the OS.  It is not within the jurisdiction of a
C program to do that.

> I've written task switching 
> programs in C under DOS that switch stacks with no problem.
> 

Neither Windows nor Linux is DOS.  What Korny said: what you're trying to do
is nuts.  Frankly I'd be surprised if gcc is even putting the asm()
statements in the resulting machine code unmolested.

> >Christopher Faylor wrote:
> 
> >I would expect that a multi-threaded linux app would not 
> like the above. 
> 
> That may well be, but I can't see why. Multiple threads 
> generally are just saving and restoring the registers, and 
> don't care what stack those registers point to. In the old 
> days with user space threading, I presume the user space code 
> would be doing what I'm trying to do and creating its own stack.
> 

This ain't the Good Old Days, and you're not writing a task switcher, which
is the only legitimate reason to be doing what you're trying to do.

-- 
Gary R. Van Sickle
 


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