Syntax for Attribute Specifications

The syntax for an attribute specification is

__attribute__((
  list-of-attributes ))
  

where list-of-attributes is a comma-separated list of zero or more attributes to associate with the object. Place an attribute specification at the end of the delcaration and definition of a function, function parameter, or variable. Example of an attribute specification shows an example.

int f(int x __attribute__((unused))) __attribute__((never_inline));

int f(int x __attribute__((unused))) __attribute__((never_inline))
{
   return 20;
}

• __attribute__((noreturn))
  Specifies that a function will never return if it is called.
• __attribute__((deprecated))
  Specifies that the compiler must issue a warning when a program refers to an object.
• __attribute__((force_export))
  Prevents a function or static variable from being dead-stripped.
• __attribute__((malloc))
  Specifies that the pointers returned by a function will not point to objects that are already referred to by other variables.
• __attribute__((noalias))
  Prevents access of data object through an indirect pointer access.
• __attribute__((returns_twice))
  Specifies that a function may return more than one time because of multithreaded or nonlinear execution.
• __attribute__((unused))
  Specifies that the programmer is aware that a variable or function parameter is not referred to.
• __attribute__((used))
  Prevents a function or static variable from being dead-stripped.
• __attribute__((never_inline))
  Specifies that a function must not be inlined.