Doxygen : handling unused function parameters with "UNUSED" macro - doxygen

Question

Short version
To prevent the compiler from raising a warning about unused variables I define the macro UNUSED as:
UNUSED(x)=x __attribute__((__unused__))
This macro is then employed in some functions' prototypes, for instance :
void ext(int foo, int UNUSED( bar ) )
However, doxygen is unhappy about that and returns some warnings:
/tmp/sandbox/main.cpp:13: warning: argument 'bar' of command #param is not found in the argument list of Dummy::ext(int foo, intUNUSEDbar)
/tmp/sandbox/main.cpp:13: warning: The following parameters of Dummy::ext(int foo, intUNUSEDbar) are not documented:
parameter 'UNUSED'
How should I tell doxygen to ignore the UNUSED macro ?
Long version
I have a code that looks like the following :
#include <iostream>
class Dummy
//! Dummy class
{
public :
//!Dummy function
/**
* \param foo First variable
* \param bar Second variable
*/
void ext(int foo, int UNUSED( bar ) )
{
std::cout << "foo = " << foo << std::endl;
}
};
//!Main function
int main(void)
{
Dummy MyDummy;
MyDummy.ext(1, 2);
return 0;
}
I compile it by invoking :
g++ -D 'UNUSED(x)=x __attribute__((__unused__))' main.cpp
To generate the default doxygen configuration file named Doxyfile I enter :
doxygen -g
Eventually, to generate the documentation I enter :
doxygen Doxyfile
The latter command outputs the following warning :
/tmp/sandbox/main.cpp:13: warning: argument 'bar' of command #param is not found in the argument list of Dummy::ext(int foo, intUNUSEDbar)
/tmp/sandbox/main.cpp:13: warning: The following parameters of Dummy::ext(int foo, intUNUSEDbar) are not documented:
parameter 'UNUSED'

Answer 1

Following instructions from the doxygen documentation, modify the Doxyfile so that it has the following parameters :
#Doxygen will run its own preprocessor before parsing the file
ENABLE_PREPROCESSING = YES
#The Doxygen preprocessor will not only define the macros (default
#behaviour) but also expand them
MACRO_EXPANSION = YES
#The Doxygen preprocessor will only expand the macros that are listed in
#the PREDEFINED setting. Any other macro will merely be defined, and not
#expanded.
EXPAND_ONLY_PREDEF = YES
#The Doxygen preprocessor will replace any occurrence of the UNUSED
#macro by its argument
PREDEFINED = UNUSED(x)=x
After those changes, invoking doxygen Doxyfile no longer raises warnings.