On Sat, Nov 14, 2009 at 1:21 PM, Brian Wang <brian.wang.0...@gmail.com> wrote:
> On Sat, Nov 14, 2009 at 1:44 AM, Gustavo Sverzut Barbieri
> <barbi...@profusion.mobi> wrote:
>> On Fri, Nov 13, 2009 at 3:13 PM, Brian Wang <brian.wang.0...@gmail.com>
>> wrote:
>>> On Fri, Nov 13, 2009 at 8:12 PM, Gustavo Sverzut Barbieri
>>> <barbi...@profusion.mobi> wrote:
>>>> On Fri, Nov 13, 2009 at 4:49 AM, Brian Wang <brian.wang.0...@gmail.com>
>>>> wrote:
>>>>> [snip]
>>>>>> OK. With the help of gdbserver/gdb, I am able to find where it's
>>>>>> looping.
>>>>>> However, I don't know what causes it. Here it goes:
>>>>>> [svn r43601]
>>>>>> evas/src/lib/canvas/evas_object_textblock.c:3152
>>>>>
>>>>> The line number is off... I've put some of my stuff in the front of
>>>>> the source code... My bad.
>>>>>
>>>>>> evas_object_textblock_text_markup_get() calls
>>>>>> escape = _escaped_char_match(p, &adv);
>>>>>> _escaped_char_match() returns "" and 'adv' is set to 0
>>>>>> thus the looping.
>>>>>>
>>>>>> Here is the gdb backtrace:
>>>>>> --------------------------------------
>>>>>> (gdb) bt
>>>>>> #0 _escaped_char_match (s=0x780a1 "追 ", adv=0xbec8c490)
>>>>>> at evas_object_textblock.c:2732
>>>>>> #1 0x4008338c in evas_object_textblock_text_markup_get (obj=0x75380)
>>>>>> at evas_object_textblock.c:3152
>>>>>> #2 0x40826be0 in _edje_part_recalc_single (ed=0x0, ep=0x0, desc=0x75ae0,
>>>>>> chosen_desc=0x40300000, rel1_to_x=0x0, rel1_to_y=0x40884c2c,
>>>>>> rel2_to_x=0x3, rel2_to_y=0x751c0, confine_to=0x0, params=0x749ac,
>>>>>> flags=3)
>>>>>> at edje_calc.c:651
>>>>>> #3 0x408271c8 in _edje_part_recalc (ed=0x10, ep=0x748bc, flags=1)
>>>>>> at edje_calc.c:1721
>>>>>> #4 0x40828e10 in _edje_recalc_do (ed=0x780a1) at edje_calc.c:224
>>>>>> #5 0x408473b4 in edje_object_size_min_restricted_calc (
>>>>>> obj=<value optimized out>, minw=0x0, minh=0x4025e27c, restrictedw=0,
>>>>>> restrictedh=-1) at edje_util.c:2362
>>>>>> #6 0x40847618 in edje_object_size_min_calc (obj=0x780a1,
>>>>>> minw=0xbec8c490,
>>>>>> minh=0x40144860) at edje_util.c:2311
>>>>>> #7 0x40210a6c in _sizing_eval (obj=0x5d060) at elm_label.c:55
>>>>>> #8 0x40210e10 in elm_label_label_set (obj=0x5d060, label=0x8c88 " 追 ")
>>>>>> at elm_label.c:121
>>>>>> #9 0x00008b1c in elm_main (argc=1, argv=0xbec8cd04) at
>>>>>> elm-label-bug-test.c:36
>>>>>> #10 0x00008bac in main (argc=1, argv=0xbec8cd04) at
>>>>>> elm-label-bug-test.c:64
>>>>>> --------------------------------------
>>>>>>
>>>>>> I don't know what's special about the string that makes it end up the
>>>>>> condition.
>>>>>> Checking if (strlen(escape)==0 && adv==0) seems to terminate the loop.
>>>>>> But I totally have no clue what's going on here... Fixing it without
>>>>>> knowing what's causing the condition is wrong.
>>>>>>
>>>>>> The string "追 " in UTF-8 is of value: 0xe8 0xbf 0xbd 0x20
>>>>>>
>>>>>> Is the info above enough to track down the problem?
>>>>>
>>>>> I've tracked it down a bit.
>>>>> On x86, via gdb,
>>>>> ------------------------
>>>>> (gdb) p escape_strings[sizeof(escape_strings)]
>>>>> $4 = 102 'f'
>>>>> ------------------------
>>>>>
>>>>> On my arm, via gdb,
>>>>> ------------------------
>>>>> (gdb) p escape_strings[sizeof(escape_strings)]
>>>>> $12 = 0 '\0'
>>>>> ------------------------
>>>>
>>>> As you said below, it is invalid read.
>>>>
>>>>
>>>>> At the very last check of
>>>>> while ((*mc) && (*sc)),
>>>>> map_itr is equal to map_end and the difference is the on x86 *mc is
>>>>> non-zero and on my arm, *mc is zero.
>>>>> Therefore, on arm, the while loop is skipped all together and 'match'
>>>>> is still 1. And hence the looping...
>>>>>
>>>>> sizeof(escape_strings) on both platforms are the same: 1551.
>>>>> I would say that it is invalid read for both cases. The x86 case gets
>>>>> lucky and got away with it.
>>>>> I'm surprised that valgrind did not catch this. Or maybe I'm wrong...
>>>>> char a[] = "s";
>>>>> sizeof(a) == 2
>>>>> accessing a[2] is out of bounds
>>>>
>>>> this is correct. As why it does not warn, maybe there is another valid
>>>> string allocated right after, thus you end reading something valid and
>>>> valgrind will not warn you.
>>>
>>> I guess so too. I thought valgrind is pretty good at catching
>>> out-of-bounds accesses..
>>
>> well, there are some flags to make GCC produce code with garbage
>> before and after arrays, I guess it's fortify source or something like
>> that. mudflap should help as well.
>>
>>
>>>>> We may check if (map_itr < map_end) after the first
>>>>> _advance_after_end_of_string() inside _escaped_char_match()
>>>>> or we may decrease map_end by 1 since every escape character is
>>>>> already terminated by a null character.
>>>>> Thus, my proposed patch (sorry for the bad part at the front, which is
>>>>> only for my own usage):
>>>>> ------------------------------------------------
>>>>> Index: src/lib/canvas/evas_object_textblock.c
>>>>> ===================================================================
>>>>> --- src/lib/canvas/evas_object_textblock.c (revision 43601)
>>>>> +++ src/lib/canvas/evas_object_textblock.c (working copy)
>>>>> @@ -1608,6 +1608,18 @@
>>>>> _layout_word_start(char *str, int start)
>>>>> {
>>>>> int p, tp, chr = 0;
>>>>> +
>>>>> +#if 1
>>>>> + //
>>>>> + // coolbrian: break if the word is not within the ASCII range
>>>>> + // @note This is good for breaking up Chinese words, which are
>>>>> made of Chinese characters.
>>>>> + // Chinese characters do not look strange if they are not
>>>>> grouped to form a 'phrase'.
>>>>> + // Also, Chinese 'phrases' are of too many patterns and
>>>>> probably need a dictionary to look up.
>>>>> + // That would be too much.
>>>>> + //
>>>>> + if (((unsigned char)str[start]) >= 0x80)
>>>>> + return start;
>>>>> +#endif
>>>>>
>>>>> p = start;
>>>>> chr = evas_common_font_utf8_get_next((unsigned char *)(str), &p);
>>>>> @@ -2709,7 +2721,7 @@
>>>>> const char *map_itr, *map_end, *mc, *sc;
>>>>>
>>>>> map_itr = escape_strings;
>>>>> - map_end = map_itr + sizeof(escape_strings);
>>>>> + map_end = map_itr + sizeof(escape_strings) - 1;
>>>>>
>>>>> while (map_itr < map_end)
>>>>
>>>> It's weird:
>>>>
>>>> map_end = map_itr + sizeof(escape_strings)
>>>>
>>>> is fine, as we compare for less than, so this address would never be
>>>> used. The last run should be on escape_strings:
>>>> "⊥\0" "\xe2\x8a\xa5\0"
>>>>
>>>> Thus:
>>>>
>>>> while (map_itr < map_end)
>>>>
>>>> --> yes, we're at map_itr = ⊥\0
>>>>
>>>>
>>>> {
>>>> const char *escape;
>>>> int match;
>>>>
>>>> escape = map_itr;
>>>>
>>>> --> escape = ⊥\0
>>>>
>>>>
>>>> _advance_after_end_of_string(&map_itr);
>>>> mc = map_itr;
>>>>
>>>> --> map_itr = \xe2\x8a\xa5\0
>>>>
>>>>
>>>> sc = s;
>>>> match = 1;
>>>> while ((*mc) && (*sc))
>>>> {
>>>>
>>>> --> enters
>>>>
>>>>
>>>> if ((unsigned char)*sc < (unsigned char)*mc) return NULL;
>>>>
>>>> --> I have no clue why this
>>>
>>> I don't either...
>>>
>>>>
>>>>
>>>> if (*sc != *mc) match = 0;
>>>>
>>>> --> fails, thus match = 0
>>>>
>>>>
>>>> mc++;
>>>> sc++;
>>>> }
>>>> if (match)
>>>>
>>>> --> skipped, as match = 0
>>>>
>>>> {
>>>> *adv = mc - map_itr;
>>>> return escape;
>>>> }
>>>> _advance_after_end_of_string(&map_itr);
>>>>
>>>> --> map_itr was \xe2\x8a\xa5\0, thus it's now one byte after, thus
>>>> map_itr == escape_strings + sizeof(escape_strings) and thus the next
>>>> while (map_itr < map_end) will fail.
>>>
>>> No. map_itr == escape_strings + sizeof(escape_strings) -1
>>> Thus the next while (map_itr < map_end) will pass.
>>
>> So that's the bug. If map_itr was \xe2\x8a\xa5\0 and
>> _advance_after_end_of_string(&map_itr); looks for the first \0 (the
>> last char) then increments one, we clearly should be correct! :-(
>>
>>
>>> If we simplify the string a bit:
>>> char escape_strings[] = "\xe2\x8a\0"; // sizeof it == 4
>>> say escape_strings is at address 0x0
>>> map_itr = 0;
>>> map_end = 0 + 4 = 4;
>>> _advance_after_end_of_string(&map_itr);
>>> map_itr=3;
>>
>> what?! how advance after of string is returning 3???
>> it should read 3 times, stop since it found 0, then increment one...
>> please debug that one :-)
>
> static void _advance_after_end_of_string(const char **p_buf)
> {
> while (**p_buf != 0) (*p_buf)++;
> (*p_buf)++;
> }
>
> After the while loop, *p_buf=2 (read 3 times but the 3rd time does not
> increment it). The second line would make it 3.
> Please have a look at the attached file.
Sorry for replying to my own mail.
Is it a non-bug? Or am I looking at the wrong spot?
Thanks for the feedbacks. :-)
brian
>
>>
>>
>> --
>> Gustavo Sverzut Barbieri
>> http://profusion.mobi embedded systems
>> --------------------------------------
>> MSN: barbi...@gmail.com
>> Skype: gsbarbieri
>> Mobile: +55 (19) 9225-2202
>>
>
>
>
> --
> brian
> ------------------
>
> Cool-Karaoke - The smallest recording studio, in your palm, open-sourced
> http://cool-idea.com.tw/
>
> iMaGiNaTiOn iS mOrE iMpOrTaNt tHaN kNoWlEdGe
>
--
brian
------------------
Cool-Karaoke - The smallest recording studio, in your palm, open-sourced
http://cool-idea.com.tw/
iMaGiNaTiOn iS mOrE iMpOrTaNt tHaN kNoWlEdGe
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