I am using a message handler class that implements amongst others:

static void message ( std::string aHeader,
std::string aMessage,
int aTimeout = 0,
MessageType aFlag =
MSG_Information );

I then use a set of defines, e.g.:

#define USR_MSG( msg ) MSG::message( "", msg, 0, MSG_User )

The problem is now that I get a compiler error when I write

USR_MSG("The value of x is " << x);

Does anybody have a smart solution for that? I thought about rerouting
std::cout but it doesn't seem to be the best way to me.

Thanks a lot for your help,

Martin.

In article <1178602787.457440.313660@h2g2000hsg.googlegroups.com>,
gmail.com> wrote:

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newsreaders will remove the clc++m banner automatically. -mod }

probstm@gmail.com wrote:

You would always get a compile error when you write

"x is " << x

in a context where that is evaluated as is. FYI: in the context of

std::cout << "x is " << x << std::endl;

the expressions are evaluated as

(((std::cout << "x is ") << x) << std::endl);

It's bad idea to use 'os' as the name of temporary object inside
macro. Consider this example:

std::string os = "Linux";
USR_MSG("Running on " << os); // You are doomed

Here USR:message will be called with second parameter equal to
something like "Running on 0012FEF8". This bug can be really hard one
to track down.

Conclusion: always use loooooong and low-chance-to-occur-in-user-code
names inside macros. Using __LINE__ as a part of the name is also a
good idea.

Roman Perepelitsa.