The free function, which deallocates heap memory, may accept a NULL pointer and take no action. Therefore, it is unnecessary to check the argument for the value of NULL before a function call to free. As such, these guards may hinder performance and readability.

A function call to free should not depend upon the value of its argument. Delete the condition preceding a function call to free when its only purpose is to check the value of the pointer to be freed.

In this example, the condition checking the value of foo can be deleted.
  • The Open Group Base Specifications Issue 7, 2018 Edition: free - free allocated memory.