Re: a question about memory access on IA64

[Martin Pool <mbp@sourcefrog.net>]

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Please reply to the list, not to me.

On 16 Jan 2004, liuduo <liuduo@sinosoft.com.cn> wrote:
> Martin Pool wrote:
> >On 16 Jan 2004, liuduo <liuduo@sinosoft.com.cn> wrote:
> >>David:
> >>Sorry, i only describe the process about the error occurs .
> >>
> >>  typedef struct b{
> >>    char*  pDescriptName;
> >>    char*           pVendorName;
> >>    unsigned int	RevisionID;
> >>   }B;
> >>
> >>  typedef struct pci{
> >>   int c;
> >>   struct b bb[512];
> >>   }PCI;
> >>
> >>int main()
> >>{
> >>
> >>
> >>   struct pci a;
> >>
> >>   //function for operation a
> >>   func(&a);
> >>   return 0;
> >>}
> >>
> >
> >>the func is in an lib, it's an lib export function, and the func is as 
> >>follows;
> >>
> >
> >Do you mean that it works if you use the first struct definition, and
> >if you pu the func into the same file? 
> >
> yes
> 
> >Does it have to be in a
> >library to fail?
> >
> yes
> 
> >
> >
> >Could it be that you are using different structure packing for
> >building the library, either through compiler options or #pragmas in
> >some other header file?
> >
> we use the #pragma pack (1)  in the file that the func is in it.

Don't do that then.  If you access a struct with different packing
conventions, your program will lose its fingers.

> >>func(struct pci* a)
> >>{
> >>    char tmp[256];
> >>   for(num=0;num<512;num++)
> >>   {
> >>    a->bb[num].pDescriptName = (char*)malloc(100);
> >>    strcpy(a->bb[num].pDescriptName , "dddd");
> >>    a->bb[num].pVendorName = (char*)malloc(100);
> >>    strcpy(a->bb[num].pVendorName , "fffff");
> >>    a->bb[num].RevisionID = 22;
> >>   }
> >>   a->c = 512;
> >>}
> >>when call the func , the segmentation fault occurs,
> >>and then we modified the struct A as follows
> >>   typedef struct pci{
> >>   struct b bb[512];
> >>   int c;
> >>   }PCI;
> >>it's normal.
> >>please tell me why?
> >>thanks a lot.

-- 
Martin

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