c - why cant i manage ~382MB of memory when i have it available? -

objective: manage unsigned long tombola[5][10000000];

$top gives me:

top - 14:05:35  4:06,  4 users,  load average: 0.46, 0.48, 0.44 tasks: 182 total,   1 running, 180 sleeping,   1 stopped,   0 zombie cpu(s): 14.4%us,  2.4%sy,  0.0%ni, 82.5%id,  0.6%wa,  0.0%hi,  0.0%si,  0.0%st mem:   3092064k total,  1574460k used,  1517604k free,   168944k buffers swap:  1998840k total,        0k used,  1998840k free,   672756k cached 

program has, malloc size of (5*10000000) * 8bytes =382mb, fill 0s , read of stored in tombola:

long int **tombola;  if((tombola=(long int **)malloc(5))==null){ /*malloc()*/     printf("\n\tmemory error-1");     exit(1); } for(i=0;i<5;i++){     if((tombola[i]=(long int *)malloc(10000000*sizeof(long int)))==null){         printf("\n\tmemory error-2");         exit(1);     } }                                          /*malloc()*/ for(i=0;i<5;i++){     for(j=0;j<10000000;j++){         tombola[i][j]=0;     } }                                         /*fill 0s before using*/ for(i=0;i<5;i++){     for(j=0;j<10000000;j++){         printf("%ld ",tombola[i][j]);     } printf("\n\n\n\n\n"); }                                         /*control of 0s*/ 

gdb gives

program received signal sigsegv, segmentation fault. _int_malloc (av=<value optimized out>, bytes=<value optimized out>) @ malloc.c:4708 4708    malloc.c: no such file or directory.     in malloc.c (gdb) bt #0  _int_malloc (av=<value optimized out>, bytes=<value optimized out>) @ malloc.c:4708 #1  0x001dfd4c in *__gi___libc_malloc (bytes=40000000) @ malloc.c:3660 #2  0x0804ca86 in main () (gdb)  

about memory, doing or assuming wrong ??

this:

tombola=(long int **)malloc(5)) 

is wrong, it's allocating 5 bytes, leading immediate buffer overrun when treat array of 5 pointers (needing 20 bytes). meant:

tombola = malloc(5 * sizeof *tombola); 

to 5 pointers unsigned long.

note there's no point in doing dynamically, it's way simpler say:

unsigned long *tombola[5]; 

also:

1. get rid of casts of malloc()'s return value.
2. stop using magical constants (the solution above makes 5 go away in rest of code, since can use sizeof tombola / sizeof *tombola in place of 5).