My C arrays are too large

Eliot Moss moss@cs.umass.edu
Wed Sep 18 20:46:00 GMT 2019


On 9/18/2019 4:35 PM, Jose Isaias Cabrera wrote:
> 
> Joel Rees, on Wednesday, September 18, 2019 02:38 PM, wrote...
>>
>> 2019年9月14日(土) 3:50 Jose Isaias Cabrera, on
>>Moss
>>> Achim Gratz, on Friday, September 13, 2019 02:39 PM, wrote...
>>>>
>>>> Blair, Charles E III writes:
>>>>> My apologies for failing to reply on-list.  I don't know how :(
>>>>>
>>>>> My machine is 64 bit, and I hope I installed the correct version of
>>> cygwin.
>>>>>
>>>>> This program:
>>>>>
>>>>> #include<stdio.h>
>>>>> int main(){char *a[50][8192];
>>>>> return 0;}
>>>>>
>>>>> compiles with gcc  (no special options) but gives "Segmentation fault".
>>>>
>>>> You are creating an automatic variable that's larger than the default
>>>> stack.  You need to enlarge the stack, either during link time or later
>>>> e.g. via
>>>>
>>>> peflags -x0x800000 a.out
>>>
>>> This is great! Thanks.
>>>
>>> But, let's talk about this a bit... Shouldn't the compiler provide some
>>> warning, and also, it should never blow up with a "Segmentation fault".  I
>>> believe there should be some type of Out Of Memory error, or something like
>>> it.  But now just blow up.  Anyone thinks like me?  Just my 102 Dominican
>>> cents ($1 = $51 Dominican). :-)
>>>
>>
>> Well, the behavior of the compiler itself is better discussed on the
>> compiler's forums, although you may need your asbestos suit when you do so.
>>
>> That said, why do you want this variable to be automatic? Why do you want
>> it allocated on the stack?
> 
> I did not say automatically.  I said that the compiler should provide some warning about the allocation being larger than the default stack.  And, it should not result in a segmentation fault, but instead, the program should error out with out of memory, or, at least, "memory allocation is larger than default stack."  Not just blow up.

Automatic here means "stack allocated" (the "auto" keyword in C, which is almost
always omitted because it is the default).   Cheers - Eliot Moss

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