malloc segfaults Fixed

Juergen Bohn
Thu Sep 4 17:15:00 GMT 2003

Thank you very much.  It works.

Only one remark: errno is still much earlier set to 12 (Not enough memory)
than x=malloc(10000) is NULL.  I don't know if this is of interest.

Is it possible to get your patch as snapshot for 1.3.22 too?


> 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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