Fw: Re: Why do these mprotect always fail?

Corinna Vinschen corinna-cygwin@cygwin.com
Wed Feb 15 12:13:36 GMT 2023

On Feb 15 11:14, w6b7rk5yu4mt25v3 via Cygwin wrote:
> Corinna Vinschen wrote:
> > cygwin-developers is for developers woking on Cygwin itself, not for
> > developers using Cygwin to develop something else. I dropped the ML
> > from the recipient list.
> > 
> > And please don't top-post. Thanks.
> > 
> > On Feb 15 09:43, w6b7rk5yu4mt25v3 via Cygwin wrote:
> > 
> > > Almost forgot, PAGE_SIZE is set to 4096. This is a Linux application,
> > > when I compile on Cygwin it complained that PAGE_SIZE is redefined but
> > > the compilation was success nevertheless. Only when I run the
> > > application, I always exited with "Unable to mprotect".
> > 
> > 
> > PAGESIZE is 64K on Cygwin. If you change that, it breaks and you can
> > keep the pieces.
> > 
> > It would be nice to send a complete, self-contained STC() in plain C,
> > so reproducing your issue is simple and doesn't require to rework
> > your code to get a running, debuggable testcase.
> PAGE_SIZE is just a naming conflict. If you change it to something
> else, JIT_PAGE_SIZE for example, it still fails.

You're misunderstanding what PAGESIZE or PAGE_SIZE means.  It's the
system page size used for mappings, and it's a fixed value defined by
the system and provided to you by the system headers and, especially,

It's *NOT* something you can just change and think the result will still
work.  Especially given that mmap doesn't know that you changed a macro
in your application code...

> The problem is Cygwin
> is not fine with the particular value 4096 but the program needs the
> value to be exactly 4096.

Sorry, but that can't work.  If the program actually demands it, it's


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