Re: chaining statements without a semicolon

 James Kanze <>
Wed, 10 Oct 2007 01:56:44 -0700
<> wrote:

I currently have a macro for logging with a definition similar to the

#define LOG shouldLog() && logStream

so that statements of this type may be written:

LOG << "some logging << endl;

I would like to add a static variable to this macro, so that the macro
expands to:

static LogObject x; x.shouldLog() && logStream

The problem is that with control statements that optionally use braces
(if, while, etc.), the multi statement approach doesn't work. Is there
any way to rewrite this (without adding a brace to the log macro and
creating an END macro) so that everything can be done in LOG?

That's not going to work anyway; you'd need a separate name
for the static variable for each invocation of the macro.
(Of course, something like "static LogObject x ## __LINE_ ;"
might be a solution.) And of course, executing the
constructor the first time you hit the statement in control
flow is going to take time.

What problem are you trying to solve? I've used a static
log object per file in the past, requiring the user to
invoke a macro at global scope to declare it, and referring
to it in the LOG macro. In practice, for small
applications, it isn't necessary; you just use one global
object. And for large applications, the macro which
declares the local object requires an argument, specifying
the subsystem, so you can configure the log differently for
different subsystems.

James Kanze (GABI Software)
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