Re: non-const reference to temporary
On 2008-08-16 04:10, WalterHoward@gmail.com wrote:
I have a disagreement with this "error". I'm constantly running into
this with g++, perhaps, hoping at some point the latest version has
changed this. For example, here's a function.
void WriteEverythingToFile( File& file, const std::string& text)
{
file.write(text);
}
The "File" can't be const in this case, for example, because in this
class, the write operation alters some data members.
Now say I just want to quickly write some stuff to a file and I don't
care about the file object persisting or leaving any extraneous
temporary variables lying around.
WriteEverythingToFile(File("AFileName.txt"), std::string("This stuff
goes into the file"));
g++ will tell me this is an error because I'm passing a non const
reference to a temporary (anonymous variable with no name).
First of all this isn't an error, except by someones overly broad
definition of error. Other people say "why would you pass a non-const
reference to something which will be modified, but you don't care
about the modification?".
It is an error because C++ does not allow passing a reference to a
temporary, and that's it. It might not be something you agree with and
in some cases it might not make much sense (like in your example). On
the other hand it is a good solution to the problem at large (if you
could create references to temporaries it could cause a lot of trouble
in other situations).
In short you can wait until hell freezes before gcc will support what
you want, or you can wait until gcc supports the C++0x standard and use
r-value references.
--
Erik Wikstr?m
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