Dave's Brain

Browse - programming tips - noop in c or c++

Date: 2010may3
Language: C/C++
Keywords: no-op

Q.  How can I do an assembler-like NOOP in C/C++ ?

A.  If you really want to do nothing you can do:

	#define NOOP		/* do nothing */

	ExampleUse()
	{
		NOOP
	}

or

	// Notice there is no trailing semicolon
	#define NOOP_FUNCTION	do { /* do nothing */ } while (false)

	ExampleUse()
	{
		NOOP_FUNCTION();
		// This might not get compiled down to nothing
	}

or 

	inline void Noop()
	{
		/* do nothing */
	}

	ExampleUse()
	{
		Noop();
	}

or

	In some environments, in <stdarg.h> you have:

	#define va_end(ap)          ((void)0)

	which does very little.

	ExampleUse()
	{
		va_end(ap);
	}

But sometimes you want a very small time delay.  So you can try:

	true;

	ExampleUse()
	{
		true;		// Sleep a bit
	}

In Windows you can do:

	Sleep(0);

	Which appears to do very little.  It will sleep zero milliseconds
	and but also give control to another process if it is waiting.

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