Re: Usage of pre-processor macro.

James Kanze <>
Sun, 4 Jul 2010 03:52:26 -0700 (PDT)
On Jun 30, 6:43 pm, =D6=F6 Tiib <> wrote:

On 30 juuni, 20:11, Pete Becker <> wrote:

On 2010-06-30 10:50:46 -0400, Christian Hackl said:

Pete Becker ha scritto:

On 2010-06-30 07:02:44 -0400, Helge Kruse said:

If you omit the UNREF_PARAM, the compiler may warn about
unreferenced parameter(s). The macro creates code where
the parameter is assigned to itself. This doesn't hurt
and is optimized away if optimization is enabled.

Turn off stupid warnings.

I often see this warning labelled as "stupid", but have
you never had a situation in which, by accident, you
really were using the wrong variable in the function?
Something along the lines of:

int MyClass::calculate(int x, int y)
  return complicatedCalculation(x, x); // bug, should be x, y

Are some "false positives" of this warning a reason to
give away a chance to automatically detect such bugs?

Yes. If you've written good unit tests, ignoring a function
argument that matters will always be detected.

Unit tests do not usually test design problems, so how they help?

Because the example error wasn't a design problem, but a typo.

Parameters that do not matter are usually present because of a design
problem. Problem is that virtual function does not manage too well
with its two responsibilities:
1) to allow polymorphism.
2) to be convenient interface.

When that problem is acknowledged (and decision is made to
ignore it) then it is OK to suppress that warning at that

A better solution would be to not name the parameter in the
functions which don't need it.

James Kanze

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