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Re: double free or corruption in base Rev. 39909 2016-06-22 16:14:05
From: |
Pirmin Braun |
Subject: |
Re: double free or corruption in base Rev. 39909 2016-06-22 16:14:05 |
Date: |
Fri, 24 Jun 2016 23:58:52 +0200 |
On Fri, 24 Jun 2016 05:55:03 +0100
Richard Frith-Macdonald <address@hidden> wrote:
> >
> >
> > but then I did the same in plain C (see Test_MariaDB_main.c) and there it
> > works. Or in other words: when I remove the ObjC runtime and the very
> > little ObjC stuff, the crash doesn't occur.
>
> That's not really telling indicative of anything ... different code has
> memory laid out differently, so overruns will write on different parts of the
> memory and cause different crashes (or often no crash at all).
> You therefore have to assume that the problem could be anywhere, and try to
> narrow it down using frequent checks (mcheck_protect etc).
> There is also the problem that adding calls to diagnostic functions could in
> itself hide the bug ... so non-intrusive methods like valgrind are also worth
> trying.
>
it's indeed the MariaDB Client Library.
Valgrind reports:
==2955== Invalid write of size 1
==2955== at 0x4E5228D: ??? (in /usr/lib/x86_64-linux-gnu/libmariadb.so.2)
==2955== by 0x4E5288D: ??? (in /usr/lib/x86_64-linux-gnu/libmariadb.so.2)
==2955== by 0x4E52B96: mysql_real_query (in
/usr/lib/x86_64-linux-gnu/libmariadb.so.2)
==2955== by 0x4007B7: executeSQL (Test_MariaDB_main.c:22)
==2955== by 0x4008C3: main (Test_MariaDB_main.c:55)
==2955== Address 0x63d4228 is 0 bytes after a block of size 8,152 alloc'd
==2955== at 0x4C28C20: malloc (vg_replace_malloc.c:296)
==2955== by 0x4E5AEE8: ??? (in /usr/lib/x86_64-linux-gnu/libmariadb.so.2)
==2955== by 0x4E58E26: ??? (in /usr/lib/x86_64-linux-gnu/libmariadb.so.2)
==2955== by 0x4E52216: ??? (in /usr/lib/x86_64-linux-gnu/libmariadb.so.2)
==2955== by 0x4E5288D: ??? (in /usr/lib/x86_64-linux-gnu/libmariadb.so.2)
==2955== by 0x4E52B96: mysql_real_query (in
/usr/lib/x86_64-linux-gnu/libmariadb.so.2)
==2955== by 0x4007B7: executeSQL (Test_MariaDB_main.c:22)
==2955== by 0x4008C3: main (Test_MariaDB_main.c:55)
on the version with the crashing query string in both test programs - ObjC and
C.
Only difference is, ObjC program crashes and C doesn't.
With the slightly modified query string valgrind reports no invalid write.
--
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