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Function/Variable Attributes
Common Utility Headers - LUFA/Drivers/Common/Common.h

Special function/variable attribute macros. More...

## Macros
#define | ATTR_ALIAS(Func) __attribute__ ((alias( #Func )))
#define | ATTR_ALIGNED(Bytes) __attribute__ ((aligned(Bytes)))
#define | ATTR_ALWAYS_INLINE __attribute__ ((always_inline))
#define | ATTR_CONST __attribute__ ((const))
#define | ATTR_DEPRECATED __attribute__ ((deprecated))
#define | ATTR_INIT_SECTION(SectionIndex) __attribute__ ((used, naked, section (".init" #SectionIndex )))
#define | ATTR_NAKED __attribute__ ((naked))
#define | ATTR_NO_INIT __attribute__ ((section (".noinit")))
#define | ATTR_NO_INLINE __attribute__ ((noinline))
#define | ATTR_NO_RETURN __attribute__ ((noreturn))
#define | ATTR_NON_NULL_PTR_ARG(...) __attribute__ ((nonnull (__VA_ARGS__)))
#define | ATTR_PACKED __attribute__ ((packed))
#define | ATTR_PURE __attribute__ ((pure))
#define | ATTR_WARN_UNUSED_RESULT __attribute__ ((warn_unused_result))
#define | ATTR_WEAK __attribute__ ((weak))

## Detailed Description

This module contains macros for applying specific attributes to functions and variables to control various optimizer and code generation features of the compiler. Attributes may be placed in the function prototype or variable declaration in any order, and multiple attributes can be specified for a single item via a space separated list.

On incompatible versions of GCC or on other compilers, these macros evaluate to nothing unless they are critical to the code's function and thus must throw a compile error when used.

## Macro Definition Documentation

#define ATTR_ALIAS | ( |  | Func | ) | __attribute__ ((alias( #Func )))

Marks a function as an alias for another function.

Parameters

  [in] | Func | Name of the function which the given function name should alias.

#define ATTR_ALIGNED | ( |  | Bytes | ) | __attribute__ ((aligned(Bytes)))

Indicates the minimum alignment in bytes for a variable or struct element.

Parameters

  [in] | Bytes | Minimum number of bytes the item should be aligned to.

#define ATTR_ALWAYS_INLINE __attribute__ ((always_inline))

Forces the compiler to inline the specified function. When applied, the given function will be in-lined under all circumstances.

#define ATTR_CONST __attribute__ ((const))

Indicates that the specified function is constant, in that it has no side effects other than parameter access.

#define ATTR_DEPRECATED __attribute__ ((deprecated))

Marks a given function as deprecated, which produces a warning if the function is called.

#define ATTR_INIT_SECTION | ( |  | SectionIndex | ) | __attribute__ ((used, naked, section (".init" #SectionIndex )))

Places the function in one of the initialization sections, which execute before the main function of the application. Refer to the avr-libc manual for more information on the initialization sections.

Parameters

  [in] | SectionIndex | Initialization section number where the function should be placed.

#define ATTR_NAKED __attribute__ ((naked))

Removes any preamble or postamble from the function. When used, the function will not have any register or stack saving code. This should be used with caution, and when used the programmer is responsible for maintaining stack and register integrity.

#define ATTR_NO_INIT __attribute__ ((section (".noinit")))

Forces the compiler to not automatically zero the given global variable on startup, so that the current RAM contents is retained. Under most conditions this value will be random due to the behavior of volatile memory once power is removed, but may be used in some specific circumstances, like the passing of values back after a system watchdog reset.

#define ATTR_NO_INLINE __attribute__ ((noinline))

Prevents the compiler from considering a specified function for in-lining. When applied, the given function will not be in-lined under any circumstances.

#define ATTR_NO_RETURN __attribute__ ((noreturn))

Indicates to the compiler that the function can not ever return, so that any stack restoring or return code may be omitted by the compiler in the resulting binary.

#define ATTR_NON_NULL_PTR_ARG | ( |  | ... | ) | __attribute__ ((nonnull (__VA_ARGS__)))

Indicates that the specified parameters of the function are pointers which should never be `NULL`. When applied as a 1-based comma separated list the compiler will emit a warning if the specified parameters are known at compiler time to be `NULL` at the point of calling the function.

#define ATTR_PACKED __attribute__ ((packed))

Marks a variable or struct element for packing into the smallest space available, omitting any alignment bytes usually added between fields to optimize field accesses.

#define ATTR_PURE __attribute__ ((pure))

Indicates that the specified function is pure, in that it has no side-effects other than global or parameter variable access.

#define ATTR_WARN_UNUSED_RESULT __attribute__ ((warn_unused_result))

Indicates that the function returns a value which should not be ignored by the user code. When applied, any ignored return value from calling the function will produce a compiler warning.

#define ATTR_WEAK __attribute__ ((weak))

Marks a function as a weak reference, which can be overridden by other functions with an identical name (in which case the weak reference is discarded at link time).