r18612 - gnucash/trunk/src - Corrections to r18610 to permit compiling against older versions of glib
warlord at MIT.EDU
Tue Feb 9 08:54:12 EST 2010
I think you missed my main point, which is that your new code *wont
work* because it never assigns the correct variable. More details
John Ralls <jralls at ceridwen.us> writes:
>>> - gnc_numeric *key;
>>> + gnc_numeric *key = NULL;
>>> + gpointer pkey = (gpointer)key;
Okay, so key is now NULL, which is fine. But then the second line
just assigns pkey to the VALUE of key, which means pkey == NULL.
>>> - while (g_hash_table_iter_next (&iter, (gpointer *)&key, NULL))
>>> + while (g_hash_table_iter_next (&iter, &pkey, NULL))
In this call, g_hash_table_iter_next() will assign the next value into
pkey. So now pkey has the new item, but key is STILL NULL.
>>> /* Compute a new reachable value */
>>> gnc_numeric reachable_value = gnc_numeric_add_fixed(*key, split_value);
And now you try to dereference key, which is still NULL. *boom*
>> Same problem here! psplit will get set, but that wont affect the value
>> of split. The original code looks just fine to me!
And you do the same thing in the second portion, too. You'll get a NULL
pointer dereference once you try to access 'split'
> The problem in both cases was that gcc-4.1.3 puked on casting the address of key to a gpointer*:
> cc1: warnings being treated as errors
> window-autoclear.c: In function ‘gnc_autoclear_window_ok_cb’:
> window-autoclear.c:171: warning: dereferencing type-punned pointer will break strict-aliasing rules
> (And, of course, the same for split.)
Fair enough. I wonder if we actually NEED the explicit cast?
If we do then we need to come up with another way of doing it,
maybe by re-assigning after the fill-in call.
> Note that I haven't changed the level of indirection passed to g_hash_table_foo; it's effectively a void** (because a gpointer is a typedef of void *) in both the old and new -- which is what g_hash_table_iter_next and g_hash_table_lookup_extended expect, so presumably they need to double-dereference.
No, you haven't. However you also haven't re-assigned the original
variable, either, which means you'll get a NULL pointer exception.
> John Ralls
Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
Member, MIT Student Information Processing Board (SIPB)
URL: http://web.mit.edu/warlord/ PP-ASEL-IA N1NWH
warlord at MIT.EDU PGP key available
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