Suppress Compiler warning Function declared never referenced

Question

So i have some code like this:

void foo (int, int);  void bar ( ) {     //Do Stuff     #if (IMPORTANT == 1)        foo (1, 2);    #endif  } 

When doing a compile without "IMPORTANT" I get a compiler Warning that foo is defined and never referenced. Which got me thinking (that is the problem).

So to fix this i just added the same #if (IMPORTANT == 1) around the function definition etc... to remove the warning, and then I started to wonder if there was a different way to suppress that warning on that function. I was looking at "unused" GCC attrib and didn't know if functions had the same attribute i could set? Is there even another way to suppress it that suppresses that warning for only that function and not the file?

Answer 1

In C++17 you can declare your function with [[maybe_unused]]:

[[maybe_unused]] void foo (int, int); 

This will suppress the warning and is the correct, idiomatic way to express a possibly unused function in C++17.

Answer 2

I'm fairly sure the relevant warning option is this one:

-Wunused-function
Warn whenever a static function is declared but not defined or a non-inline static function is unused. This warning is enabled by -Wall.

So the warning should only be given for a static function, interesting. Makes sense. If a function is static it can only be used within the current file, so its definition must also be in this file.

And declaring it static inline avoids the warning, without resorting to ugly macros or compiler-specific pragmas or attributes.