Re: malloc segfaults

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On Tue, Sep 02, 2003 at 03:35:04PM +0200, Juergen Bohn wrote:
> Tested with cygwin1.dll 1.5.3-1 and 1.3.22-1 on Win2000-SP4, malloc() does 
> not (always)
> return NULL if there is no more memory available.  Try, for example, simple 
> loops like:
> 
>   x = malloc(10000);
>   for (i=0; x != NULL; i++)
>   {
>       x = malloc(10000);
>       if (x == NULL)    printf("x is NULL\n");
>   }
> 
> My application terminates with a segmentation violation, but all attempts 

I've applied a patch to cygwin which solves this problem.  You should
get NULL at one point instead.

> to handle this by signal() or atexit() fail.  Unfortunately, also sysconf() 
> does not work to get the number of available pages (_SC_AVPHYS_PAGES, I get 
> always the same but wrong value).

I've changed sysconf to return a more accurate value for _SC_AVPHYS_PAGES.
However, this is not a value you can rely on.  Cygwin processes might run
out of memory even though there are still a lot of physical pages available.
This is related to the fact that small allocations (less than 1 Meg) are
taken from the applications heap which might be unraisable for some reason.

Corinna

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Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Developer                                mailto:cygwin@cygwin.com
Red Hat, Inc.

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