On Fri, 20 Aug 2010, Jussi Lehtola wrote:
> On Fri, 20 Aug 2010 13:22:33 -0500 (CDT)
> Michael Hennebry <hennebry@xxxxxxxxxxxxxxxxxxxxx> wrote:
>> It makes sense that if a process insists on physically
>> contiguous memory and can't get it, the process would die,
>> but the above code does not tell the compiler what is to be achieved.
>>
>> In the following, would fred or greg necessarily
>> refer to physically contiguous memory?
>>
>> #include <stdlib.h>
>> extern void hank(char *);
>>
>> int main(*args[], int argsNum)
>> {
>> char fred[69000];
>> char *greg=malloc(96000);
>> hank(fred);
>> hank(greg);
>> return 0;
>> }
>
> If I remember my Kerningham-Ritchie correctly, the answer is yes, since
> C relies on pointer arithmetic to refer to the elements of the array.
> The "fred" and "greg" variables are pointers to the beginning of the
> corresponding memory area, and referring fred[i] goes to the start of
> the array at fred, and then goes i elements forward to end up with the
> wanted element.
That is contiguous in terms of virtual memory.
Adjacent virtual addresses do not have to have adjacent physical addresses.
--
Michael hennebry@xxxxxxxxxxxxxxxxxxxxx
"Pessimist: The glass is half empty.
Optimist: The glass is half full.
Engineer: The glass is twice as big as it needs to be."
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