Re: creating unique message identifiers
On Nov 4, 2:31 pm, mliptak <Meht...@gmail.com> wrote:
On Nov 4, 2:21 pm, James Kanze <james.ka...@gmail.com> wrote:
On Nov 4, 11:54 am, mliptak <Meht...@gmail.com> wrote:
I'm trying to implement logging in my application, so that
each log message has its unique identifier, e.g.
log(identifier, text) What I want to achieve is that the
compiler screams if the log() with 'identifier' is also
used in some other place in the code which would make the
'identifier' not unique. Is that something that can be
achieved in C++?
It depends on the type of identifier, but in general, yes,
provided log is a macro. In the general case, you need a
local static variable to achieve it, and the actual
identifier won't be known until compile time. If identifier
is text, however, you can generate it with a macro using
__FILE__ and __LINE__.
What if I want to set the identifier myself, not have it
generated at compile time (using local static variable)?
You mean that you want the user to provide an indentifier, that
the compiler checks for uniqueness? The compiler can't do that
per se (at least not within a single statement), but you could
easily use it as the initializer of a local static variable,
which would check for uniqueness at runtime.
I was also thinking of using the __FILE__ and __LINE__ but the
problem is this could change when the code changes, and I need
to have the identifier fixed for each message.
The real question is what the identifier is to be used for.
Most of the time, if you need each point of invocation to have a
separate identifier, it is for some sort of tracing or
debugging, in which case, __FILE__ and __LINE__ are far more
useful than anything else you could come up with.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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