Re: valgrind complaints when running datauri

On Sun, Nov 25, 2012 at 07:46:42PM +0000, corvid wrote:
> 
> Jeremy's valgrind logs have had a couple of these recently, e.g.,
> http://starurchin.org/dillo/valgrind/5b601af9ce7facc17690b88c4323c194fded01c9.html
> 
> I found that
> - after dpidc stop
> - valgrind --leak-check=full --trace-children=yes dillo
> - going to http://jimbojw.com/wiki/index.php?title=Data_URI_Explained
> - and pasting in the second example (the percent-encoded one, not the
>   base64 one)
> gets me:
> 
> ==20817== Invalid read of size 4
> ==20817==    at 0x804AED5: dStr_insert_l (dlib.c:287)
> ==20817==    by 0x804AFB5: dStr_append_l (dlib.c:308)
> ==20817==    by 0x8049317: main (datauri.c:332)
> ==20817==  Address 0x41cbbb0 is 0 bytes after a block of size 664 alloc'd
> ==20817==    at 0x402AE29: realloc (vg_replace_malloc.c:662)
> ==20817==    by 0x804A736: dRealloc (dlib.c:53)
> ==20817==    by 0x804918B: datauri_get_data (datauri.c:273)
> ==20817==    by 0x80492E1: main (datauri.c:324)
> ==20817== 
> ==20817== 
> ==20817== Process terminating with default action of signal 11 (SIGSEGV): dumping core
> 
> 
> Valgrind has options for debugging, but I haven't had any luck with
> getting them to work so far.
> 
> I'm imagining that this might have to do with only being able to send
> part of the data at a time when everything's sluggish due to valgrind,
> but I don't know datauri/dpip well enough to go straight for the most
> likely spots...
> 
> PS I don't trust the "by 0x8049317: main (datauri.c:332)" line because
> I have -O0, and sometimes it's had some 0x40... address instead that it
> describes as being below main.

Unfortunately I can't reproduce the problem here, but I see an
issue in a_Url_decode_hex_str() (datauri.c):
In line 154 two possibly unrelated pointers are subtracted. Could
you try the following:

diff -r 74833d000780 dpi/datauri.c
--- a/dpi/datauri.couldThu Nov 15 23:09:50 2012 +0100
+++ b/dpi/datauri.couldSun Nov 25 21:52:22 2012 +0100
@@ -150,8 +150,8 @@
    }
    *dest = 0;
 
+   *p_sz = (size_t)(dest - new_str);
    new_str = dRealloc(new_str, sizeof(char) * (dest - new_str +
1));
-   *p_sz = (size_t)(dest - new_str);
    return new_str;
 }



Cheers,
Johannes