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I used the following code to find it out but I always get 1 as the answer. is there something wrong. Thanks
#include <stdio.h>
#include <stdlib.h>
int main(){
int mult = 0;
int chk =8;
do{
mult+=1;
int *p = (int*)malloc(1024*1024*1024*mult);
if(p==0){
chk =0;
}else{
free(p);
}
}while(chk !=0);
mult = mult -1;
printf("The number of gigs allocated is : %d\n",mult);
return 0;
}
Just to help, I have a 64 bit system with both windows and linux installed. Thus, is the above logic correct even though I am getting just 1 gb as the answer on a 64 bit system?
364
malloc(10) allocates 10 bytes, which is enough space for 10 chars. To allocate space for 10 ints, you could call malloc(10 * sizeof(int)) . char *cp = malloc(10); int *ip = malloc(sizeof(int));
Malloc allocates memory more than RAM.
The malloc line allocates a block of memory of the size specified -- in this case, sizeof(int) bytes (4 bytes). The sizeof command in C returns the size, in bytes, of any type. The code could just as easily have said malloc(4), since sizeof(int) equals 4 bytes on most machines.
The malloc function allocates a memory block of at least size bytes. The block may be larger than size bytes because of the space that's required for alignment and maintenance information.
If it is a 32-bit OS, then it is not surprising that the largest contiguous block would be 1GB (or somewhere between that and 2GB). On a 64-bit OS, larger blocks would be possible.
If you change your code to allocate smaller individual pieces, you will likely be able to allocate more than 1GB total.
111
These questions might help you a bit: How much memory was actually allocated from heap for an object? and How do I find out how much free memory is left in GNU C++ on Linux
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