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Thomas Mang
Guest
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 Posted: Wed Dec 29, 2004 9:08 pm Post subject: std-functions and indeterminate values |
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Hello,
Consider these fragments of code:
a)
{
int i;
std::cin >> i;
}
b)
{
char cArray[10];
std::copy(someIterator, someIterator + 10, cArray);
}
Here, both i and cArray have indeterminate value.
What I wonder is:
Is there anything that forbids std-functions (free and member) to make use
of these values other than to write?
In other words, is this pseudo-implementation (template stuff omitted) of
operator>> forbidden?
istream& istream::operator>>(int & i)
{
int someInt = i; // use of i, although probably stupid
....
}
Thank you,
Thomas
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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Mark Van Peteghem
Guest
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| Posted: Sat Jan 01, 2005 1:18 am Post subject: Re: std-functions and indeterminate values |
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Thomas Mang wrote:
| Quote: | Consider these fragments of code:
a)
{
int i;
std::cin >> i;
}
b)
{
char cArray[10];
std::copy(someIterator, someIterator + 10, cArray);
}
Here, both i and cArray have indeterminate value.
What I wonder is:
Is there anything that forbids std-functions (free and member) to make use
of these values other than to write?
|
No, there is no way this can be done in C++, for std-functions or other
functions. I recall it is possible in C#, with the 'out' specifier, but
I don't know C# that well.
Mark dot Van dot Peteghem at q-mentum dot com
http://www.q-mentum.com -- easier and more powerful unit testing
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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Thomas Mang
Guest
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| Posted: Sat Jan 01, 2005 1:21 am Post subject: Re: std-functions and indeterminate values |
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"Thomas Mang" <nospam (AT) pop (DOT) ucsd.edu> schrieb im Newsbeitrag
news:41d29c91$0$20182$3b214f66 (AT) usenet (DOT) univie.ac.at...
| Quote: |
b)
{
char cArray[10];
std::copy(someIterator, someIterator + 10, cArray);
}
|
Please substitute the char[] by another array, e.g. a double[].
Using char[] was obviously not particularly clever for
demonstration.........
However, the point remains:
Is there anything that guarantees this doesn't yield undefined behavior?
Thomas
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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Thomas Mang
Guest
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| Posted: Sat Jan 01, 2005 1:22 am Post subject: Re: std-functions and indeterminate values |
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"Thomas Mang" <nospam (AT) pop (DOT) ucsd.edu> schrieb im Newsbeitrag
news:41d29c91$0$20182$3b214f66 (AT) usenet (DOT) univie.ac.at...
| Quote: | Hello,
Consider these fragments of code:
b)
{
char cArray[10];
std::copy(someIterator, someIterator + 10, cArray);
}
|
Besides my other correction about char[], please forget this example
entirely. The specifications of the algorithm (output-iterator; requirements
/ complexity) seem to disallow any possible read-use of values.
However, the issue with operator>> remains.
Thomas
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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