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Question with regard to Volatile type specifier!

Posted on 2004-04-18
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Last Modified: 2010-04-15
Hi experts,

I'm just wondering what a volatile type specifier really does?  Is it essential in programming synchronization problem?

thanks

r6
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Question by:R6
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sunnycoder earned 34 total points
ID: 10857096
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by:ankuratvb
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by:R6
ID: 10861183
hi sunnycoder & ankuratvb,

thanks for helping me out!

heres my actual problem:

volatile struct can *theCan;
....
....


void *aFunc() {
  return theCan;
}

and the compiler signals a warning that says "warning: return discards qualifiers from pointer target type"

what does that really mean?

thank u!

r6



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Assisted Solution

by:brad_1
brad_1 earned 33 total points
ID: 10864680
You declared the return type as a "void *"  and returned a "struct can *". The mismatch between these causes the compiler to issue a warning. Either change the return type to "struct can *", or cast the returned pointer to "void *".
e.g. return (void *) theCan;

I don't know if the volatile keyword is relevant to the return type.

Brad
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by:ankuratvb
ID: 10867321
Does the warning disappear if you remove the volatile from thecan's declaration.?

I cant test it myself coz on my compiler,i dont even get a warning.

BTW,what compiler are u using?

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Expert Comment

by:ankuratvb
ID: 10867338
It shouldnt be because of the void * return type and you returning a struct can *
coz void pointers can be assigned to any kind of pointer without requiring an explicit cast and without loss of information.

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