| Topic: |
DEVELOP > c-Plus-Plus |
| User: |
"Venn Syii" |
| Date: |
10 Dec 2004 07:41:51 AM |
| Object: |
type casting problem |
I do the following:
->Lock( 0, 0, (BYTE**)&pVertices, DUSAGE_WRITEONLY )
And get the following error:
error C2664: 'Lock' : cannot convert parameter 3 from 'unsigned char ** ' to
'void ** '
Any ideas?
Regards,
Venn
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| User: "Dave OHearn" |
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| Title: Re: type casting problem |
10 Dec 2004 08:22:59 AM |
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Venn Syii wrote:
I do the following:
->Lock( 0, 0, (BYTE**)&pVertices, DUSAGE_WRITEONLY )
And get the following error:
error C2664: 'Lock' : cannot convert parameter 3 from
'unsigned char ** ' to 'void ** '
Any ideas?
Apparently BYTE is a typedef of unsigned char.
It looks like the Lock member function wants void **, not unsigned char
**. So don't use BYTE **; use void **. Check its documentation or
declaration to be sure though.
--
Dave O'Hearn
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| User: "Dave OHearn" |
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| Title: Re: type casting problem |
10 Dec 2004 08:50:59 AM |
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Dave O'Hearn wrote:
Apparently BYTE is a typedef of unsigned char.
It looks like the Lock member function wants void **, not
unsigned char **. So don't use BYTE **; use void **. Check its
documentation or declaration to be sure though.
It must be early in the morning. I forgot to note that casts to void
pointers are often implicit. So you can simply try deleting your cast.
--
Dave O'Hearn
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| User: "Victor Bazarov" |
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| Title: Re: type casting problem |
10 Dec 2004 09:05:46 AM |
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Dave O'Hearn wrote:
Dave O'Hearn wrote:
Apparently BYTE is a typedef of unsigned char.
It looks like the Lock member function wants void **, not
unsigned char **. So don't use BYTE **; use void **. Check its
documentation or declaration to be sure though.
It must be early in the morning. I forgot to note that casts to void
pointers are often implicit. So you can simply try deleting your cast.
There is a standard conversion from T* to void*, but he cannot delete
the cast (although he can certainly try), since there is no standard
conversion from T** to void**. Example:
void foo(void **p) {}
int main()
{
void *pv = 0;
foo(&pv); // OK
unsigned char *pc = 0;
foo(&pc); // error
}
Victor
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| User: "Victor Bazarov" |
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| Title: Re: type casting problem |
10 Dec 2004 08:30:08 AM |
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Venn Syii wrote:
I do the following:
->Lock( 0, 0, (BYTE**)&pVertices, DUSAGE_WRITEONLY )
And get the following error:
error C2664: 'Lock' : cannot convert parameter 3 from 'unsigned char ** ' to
'void ** '
Any ideas?
How is 'Lock' function declared? If it's a class, what the declaration
of its constructor? And why are you trying to cast '&pVertices' to
'BYTE**'? Your compiler is telling you that it expects a pointer to
a pointer to void as the third argument. What's the documentation say
about the use of the third argument?
V
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| User: "Matthias =?ISO-8859-1?Q?K=E4ppler?=" |
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| Title: Re: type casting problem |
10 Dec 2004 08:06:50 AM |
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What is the type of pVertices?
What is the specification of Lock?
What is BYTE? Some MS specific typedef for unsigned char?
Venn Syii wrote:
I do the following:
->Lock( 0, 0, (BYTE**)&pVertices, DUSAGE_WRITEONLY )
And get the following error:
error C2664: 'Lock' : cannot convert parameter 3 from 'unsigned char ** '
to 'void ** '
Any ideas?
Regards,
Venn
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