Inconsistency bugs in array example for libpmemobj

[dibang2008]

ISSUE: Inconsistency bugs in array example for libpmemobj

Environment Information

• PMDK package version(s): 1.9
• OS(es) version(s): Ubuntu 16 LTS
• ndctl version(s): 58+
• kernel version(s): 4.4.0-173-generic
• compiler, libraries, packaging and other related tools version(s):

Please provide a reproduction of the bug:

It exists inconsistency bugs if calling following command.
./array /mnt/pmem/testfile alloc test2 100 int

How often bug is revealed: Always:

Actual behavior:

When a crash happens in a specified place, it causes inconsistency.

Expected behavior:

It always keeps consistent.

Details

• First, line info->array= alloc_array\[type\](size); in Snippet C calls alloc_int in Snippet B and finally reaches Snippet A's alloc_int .
• Then, the crash happens in specified place of Snippet A (right before return).
• As a result, data of the array are persistent but previous info in Snippet C doesn't guarantee persistency. So it causes inconsistency

Snippet A

alloc_int(size_t size)
{
TOID(int) array;
/*
* To allocate persistent array of simple type is enough to allocate
* pointer with size equal to number of elements multiplied by size of
* user-defined structure.
*/
POBJ_ALLOC(pop, &array, int, sizeof(int) * size,
NULL, NULL);
if (TOID_IS_NULL(array)) {
fprintf(stderr, "POBJ_ALLOC\n");
return OID_NULL;
}
for (size_t i = 0; i < size; i++)
D_RW(array)[i] = (int)i;
pmemobj_persist(pop, D_RW(array), size * sizeof(*D_RW(array)));
CRASH HAPPEN
return array.oid;
}

===============================================

Snippet B

static void
static fn_alloc alloc_array[] = {NULL, alloc_int, alloc_pmemoid, alloc_toid};

=================================================

Snippet C

do_alloc(int argc, char *argv[])
{
if (argc != 3) {
printf("usage: ./array alloc "
" \n");
return;
}
enum array_types type = get_type(argv[2]);
if (type == UNKNOWN_ARRAY_TYPE)
return;
size_t size = atoi(argv[1]);
TOID(struct array_info) array_info = find_array(argv[0]);
if (!TOID_IS_NULL(array_info))
POBJ_FREE(&array_info);
POBJ_ZNEW(pop, &array_info, struct array_info);
struct array_info *info = D_RW(array_info);
strncpy(info->name, argv[0], MAX_BUFFLEN - 1);
info->name[MAX_BUFFLEN - 1] = '\0';
info->size = size;
info->type = type;
info->array = alloc_array[type](size);
if (OID_IS_NULL(info->array))
assert(0);
pmemobj_persist(pop, info, sizeof(*info));
}

Additional information about Priority and Help Requested:

Are you willing to submit a pull request with a proposed change? (Yes, No)

Requested priority: High

[pbalcer]

You are right, thanks for reporting this.
I looked over that whole example, and I think it should be either rewritten or removed entirely.