Re: More than 2, but less than 3 GiB per process memory?

[Malte Cornils <malte@cornils.net>]

Hello Hendrik!

You wrote:
> [using more than 2 GiB memory for one process on 32bit systems]
> Actually, some kludgery might help here.
>[...]
> Near the start of your program, allocate a *huge* array on the stack, like
> 
> char * hugepointer;
> int main(...)
> {
>   char huge[1000000000];
>   hugepointer = huge;
>   restofprogram(...);
> }

That did sound interesting, unfortunately, the following program immediately 
segfaults on my machine (with "just" 580 MB allocated via the stack; the 
limit where it no longer segfaults is somewhere above 8 MB and below 9 MB):

#include <stdio.h>

char *hugepointer;

struct test {
        int t1;
        int t2;
        int t3;
        int t4;
        int t5;
        int t6;
};


int main() {
        struct test *test_p;
        int i;

        char huge[580000000]; /* 580 MB... (I have 512 MB physical RAM). 
                                                      8000000 works */
        hugepointer = huge;
        for (i = 42; i < 90000000; i += 3000000) {
                printf("Size: %d sizeof: %d total: %d MiB.\n",
                                i, sizeof(struct test),
                                i*sizeof(struct test)/(1024*1024) );
                test_p = malloc(sizeof(struct test) * i);
                if (!test_p) {
                        printf("Woopsi\n");
                        exit(1);
                }
                free(test_p);
        }
}

/* compile me with: gcc memcheck-stack.c -o memcheck-stack */