Re: [HACKERS] patch for memory overrun on Linux(i386)

>
> > >From the linux man page:
> >  For calloc() and malloc(), the value returned is a pointer
> >        to the allocated memory, which is suitably aligned for any
> >        kind of variable, or NULL if the request fails.
>
> OK, then why is electric fence telling him to make DOUBLEALIGN match
> INTALIGN?  You would think that if this change made sense, we would be
> having some Linux problems, but we don't.
>
> ---------------------------------------------------------------------------
>
>
> #if ! defined(sco)
> #define DOUBLEALIGN(LEN)\
>         (((long)(LEN) + (sizeof (double) - 1)) & ~(sizeof (double) -1))
>
> #define MAXALIGN(LEN)\
>         (((long)(LEN) + (sizeof (double) - 1)) & ~(sizeof (double) -1))
> #else
> #define DOUBLEALIGN(LEN) INTALIGN(LEN)
> #define MAXALIGN(LEN)    INTALIGN(LEN)
> #endif
>

Hi Hackers,

it seems that Linux malloc, or better libc-5.4.23 malloc, is doing what is
declared in the man page, i.e. returning "memory which is suitably aligned
for any kind of variable". I have some malloc traces and all malloc results
are aligned to double size (8 bytes):

op    caller        ptr        size
--------------------------------------------
malloc    400c32b2    080a06c8    25
malloc    400c32b2    080a06e8    13
malloc    400c32b2    080a0700    26
malloc    400c32b2    080a0720    11
malloc    400c32b2    080a0730    50
malloc    400c32b2    080a0768    14
malloc    400c32b2    080a0780    17
malloc    400c32b2    080a0798    24
malloc    400c32b2    080a07b8    27
malloc    400c32b2    080a07d8    817
malloc    400c32b2    080a0b10    11
malloc    400c32b2    080a0b20    14
malloc    400c32b2    080a0b38    164
malloc    400c32b2    080a0be0    11
malloc    400c32b2    080a0bf0    14
malloc    400c32b2    080a0c08    25
malloc    400c32b2    080a0c28    16
malloc    400c32b2    080a0c40    35
malloc    400c32b2    080a0c68    9
malloc    400c32b2    080a0c78    7

So I don't see where is the problem.

Massimo Dal Zotto

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|  Massimo Dal Zotto                e-mail:  dz@cs.unitn.it            |
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