Redundant code


In computer programming, redundant code is source code or compiled code in a computer program that is unnecessary, such as:
A NOP instruction might be considered to be redundant code that has been explicitly inserted to pad out the instruction stream or introduce a time delay, for example to create a timing loop by "wasting time". Identifiers that are declared, but never referenced, are termed redundant declarations.

Examples


int foo

The second iX*2 expression is redundant code and can be replaced by a reference to the variable iY. Alternatively, the definition int iY = iX*2 can instead be removed.
Consider:

  1. define min
int shorter_magnitude

As a consequence of using the C preprocessor, the compiler will only witness the expanded form:

int shorter_magnitude

Because the use of min/max macros is very common, modern compilers are trained to recognize and eliminate redundancy caused by their use.
There is no redundancy, however, in the following code:

  1. define max >?:)
int random

The reason is that its implementation is incorrect. If the initial call to rand, modulo range, is greater than or equal to cutoff, rand will be called a second time for a second computation of rand%range, which may result in a value that is actually lower than the cutoff. The max macro will thus not work for this function.