AN3350 datasheet(116/185 Pages) STMICROELECTRONICS

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Declaration specifications

AN3350

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Doc ID 018512 Rev 2

14.4.3

__attribute__((malloc))

Specifies that the pointers returned by a function will not point to objects that are already

referred to by other variables.

Syntax

function-declaration __attribute__((malloc));

function-definition __attribute__((malloc));

Remarks

This attribute specification gives the compiler extra knowledge about pointer aliasing so that

it can apply stronger optimizations to the object code it generates.

14.4.4

__attribute__((noalias))

Prevents access of data object through an indirect pointer access.

Syntax

function-parameter __attribute__((noalias));

variable-declaration __attribute__((noalias));

variable-definition __attribute__((noalias));

Remarks

This attribute specifies to the compiler that a data object is only accessed directly, helping

the optimizer to generate a better code. The sample code in Example 72 will not return a

correct result if ip is pointed to a.

Example 72 Example of the noalias attribute

extern int a __attribute__((noalias));

int f(int *ip)

{

a = 1;

*ip = 0;

return a;

// optimized to return 1;

}

14.4.5

__attribute__((returns_twice))

Specifies that a function may return more than one time because of multithreaded or non-

linear execution.

Syntax

function-declaration __attribute__((returns_twice));

function-definition __attribute__((returns_twice));

AN3350 Datasheet(PDF) 116 Page - STMicroelectronics