Xen devel - Dec 2007 - possible bug on libxc ? on amd64

In function  :

 

Elf64_Shdr*

xc_core_shdr_get(struct xc_core_section_headers *sheaders) {

    Elf64_Shdr *shdr;

 

    if ( sheaders->num == sheaders->num_max )

    {

        Elf64_Shdr *shdrs;

        if ( sheaders->num_max + SHDR_INC < sheaders->num_max ) 
<--- in
this point 

 

 

// I think at this point ,sheaders->num_max + SHDR_INC always is major or
equal than sheaders->num_max  

 

// I think : x + y > x     

 

My consideration was only for resolving error compiling because I not have
time to learn what libxc are and what I can use function

 

J

 

 

 

       {

            errno = E2BIG;

            return NULL;

        }

 

        sheaders->num_max += SHDR_INC;

        shdrs = realloc(sheaders->shdrs,

                        sizeof(sheaders->shdrs[0]) * sheaders->num_max);

 

 

        if ( shdrs == NULL ) <<-- word wrap ??

            return NULL;

        sheaders->shdrs = shdrs;

 

 

i think this are correct: 

 

       if ( shdrs == NULL ) return NULL; 

 

        sheaders->shdrs = shdrs;

 

 

or:

 

 

if ( shdrs == NULL ) {return NULL};

        sheaders->shdrs = shdrs;

 

    }

 

    shdr = &sheaders->shdrs[sheaders->num];

    sheaders->num++;

    memset(shdr, 0, sizeof(*shdr));

    return shdr;

}

 

 

Always happy c++

 

Ps.

C++ are always better than other J 

 

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

 

Maniciati Enrico

Consulenza,progettazione,

realizzazione e assistenza

reti e sistemi informatici

 

email: e <mailto:enrico.maniciati@virgilio.it> nrico.maniciati@virgilio.it

Skype: erikm.project

Msn:  <mailto:enrico.maniciati@hotmail.it> enrico.maniciati@hotmail.it

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On Sat, 2007-12-01 at 16:25 +0100, Enrico Maniciati wrote:
> In function  :
> xc_core_shdr_get(struct xc_core_section_headers *sheaders) {
>     if ( sheaders->num == sheaders->num_max )
>     {
>         Elf64_Shdr *shdrs;
>         if ( sheaders->num_max + SHDR_INC < sheaders->num_max ) 
<---
> in this point 
sorry, good point, but this is a test against integer wrap.
>        {
>             errno = E2BIG;
>             return NULL;
>         }
>         sheaders->num_max += SHDR_INC;
num max is a 16bit integer, SHDR_INC is def''d to 4.
the function allocates up to 65532 entries, then num_max wraps to zero
and it reports failure. it''s probably okay like this.
>         shdrs = realloc(sheaders->shdrs,
>                         sizeof(sheaders->shdrs[0]) *
> sheaders->num_max);
>         if ( shdrs == NULL ) <<-- word wrap ??
no, this means out of memory.
> i think this are correct: 
[...]

quite frankly, with the exception of variants in bracing and indentation
i don''t see the difference.
> Always happy c++
> C++ are always better than other J 
thanks for all the hints. 

a tip in return: check out the ''diff'' command (supposed
you''ve got
cygwin or similar installed). works approximately like this:

	$ cp xc_core.c xc_core.c.orig
	/* .. edit xc_core.c */
	$ diff xc_core.c.orig xc_core.c > xc_core.c.diff

the resulting .diff-file is what best suited to send to mailing lists in
order to suggest buf fixes or improvement to source code.

thanks and regards,
daniel


-- 
Daniel Stodden
LRR     -      Lehrstuhl für Rechnertechnik und Rechnerorganisation
Institut für Informatik der TU München             D-85748 Garching
http://www.lrr.in.tum.de/~stodden         mailto:stodden@cs.tum.edu
PGP Fingerprint: F5A4 1575 4C56 E26A 0B33  3D80 457E 82AE B0D8 735B



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