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Gianluca Silvestri
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 Posted: Wed Sep 14, 2005 5:32 am Post subject: Writing to an unopened ofstream |
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Hi guys,
Could anyone tell me what is the effect of the code below, according to the
Standard?
#include <fstream>
#include <ostream>
int main()
{
std::ofstream os;
os << "Hello world!" << std::endl;
}
Is this UB? Or should the operator<< fail?
Thanks
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Gianluca Silvestri
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kanze
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| Posted: Wed Sep 14, 2005 2:40 pm Post subject: Re: Writing to an unopened ofstream |
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"Gianluca Silvestri" wrote:
| Quote: | Could anyone tell me what is the effect of the code below,
according to the Standard?
#include
#include
int main()
{
std::ofstream os;
os << "Hello world!" << std::endl;
}
|
Nothing. The badbit is set in os, but since you never test it,
that has no effect on anything.
| Quote: | Is this UB? Or should the operator<< fail?
|
No undefined behavior. The operator<< calls sputc on the
filebuf, which (the first time, at least) calls overflow, which
returns EOF is ! is_open(). By convention, any time sputc
returns EOF, an output stream sets badbit.
--
James Kanze GABI Software
Conseils en informatique orientée objet/
Beratung in objektorientierter Datenverarbeitung
9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34
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