Re: [Valgrind-users] valgring whith JudyArray

[Salim S. <ssa...@ti...>]

> > ==21866== Invalid read of size 4
> > ==21866==    at 0x402702E4: JudySLIns (src/JudySL/JudySL.c:630)
> > ==21866==    by 0x8048789: main (judySL_test.c:20)
> > ==21866==    by 0x40296686: __libc_start_main
(../sysdeps/generic/libc-start.c:129)
> > ==21866==    by 0x8048630: (within /home/ocadmin/salim/lab_RD/a.out)
> > ==21866==    Address 0x40D35020 is 4 bytes before a block of size 7
alloc'd
> > ==21866==    at 0x4002BB60: malloc (vg_replace_malloc.c:153)
> > ==21866==    by 0x40270009: JudySLIns (src/JudySL/JudySL.c:552)
> > ==21866==    by 0x8048789: main (judySL_test.c:20)
> > ==21866==    by 0x40296686: __libc_start_main
(../sysdeps/generic/libc-start.c:129)
> > ==21866==
> > ==21866== Invalid free() / delete / delete[]
> > ==21866==    at 0x4002BE5B: free (vg_replace_malloc.c:231)
> > ==21866==    by 0x40270378: JudySLIns (src/JudySL/JudySL.c:639)
> > ==21866==    by 0x8048789: main (judySL_test.c:20)
> > ==21866==    by 0x40296686: __libc_start_main
(../sysdeps/generic/libc-start.c:129)
> > ==21866==    Address 0x40D35020 is 4 bytes before a block of size 7
alloc'd
> > ==21866==    at 0x4002BB60: malloc (vg_replace_malloc.c:153)
> > ==21866==    by 0x40270009: JudySLIns (src/JudySL/JudySL.c:552)
> > ==21866==    by 0x8048789: main (judySL_test.c:20)
> > ==21866==    by 0x40296686: __libc_start_main
(../sysdeps/generic/libc-start.c:129)
> > File 'judySL_test.c', line 20: JudySLIns(), JU_ERRNO_* == 7, ID == 396
>
> Assuming your test program isn't buggy,
> you may have found a bug in the Judy library.
> Either way, you probably want to take this up on the Judy mailing list...
> - Dan


It seems that the pointers used in Judy array are aligned on 8 bytes!  And
launching valgrind with the option --alignment=8 solves the problem.


This paragraph, from "Judy IV Shop Manual",  explains the mystery:

----------------------------------------------------------------------------
------------

4.2 Judy Array Pointer (JAP):
A Judy Array Pointer (root pointer) is 1 word = 4 bytes [8 bytes] containing
an ordinary pointer

(memory address) that points to a Judy array, except that it always
references an object aligned to

at least a 2-word = 8-byte [16-byte] boundary. Hence the 3 [or 4] least
significant bits of the root

pointer would always be 0, and are usable to encode the type of object to
which the root pointer

points. [In fact only the least 3 bits are needed and used, even on 64-bit
systems.]



Best regards,

__salim