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AN3350

Declaration specifications

Doc ID 018512 Rev 2

117/185

Remarks

This attribute specifies to the compiler that the program’s flow of execution might enter and

leave a function without explicit function calls and returns. For example, the standard

library’s setjmp() function allows a program to change its execution flow arbitrarily.

With this information, the compiler limits optimizations that require explicit program flow.

14.4.6

__attribute__((unused))

Specifies that the programmer is aware that a variable or function parameter is not referred

to.

Syntax

function-parameter __attribute__((unused));

variable-declaration __attribute__((unused));

variable-definition __attribute__((unused));

Remarks

This attribute specifies that the compiler should not issue a warning for an object if the

object is not referred to. This attribute specification has no effect if the compiler’s unused

warning setting is off.

Example 73 Example of the unused attribute

void f(int a __attribute__((unused))) /* No warning for a. */

{

int b __attribute__((unused)); /* No warning for b. */

int c; /* Possible warning for c. */

return 20;

}

14.4.7

__attribute__((used))

Prevents a function or static variable from being dead-stripped.

Syntax

function-declaration __attribute__((used));

function-definition __attribute__((used));

variable-declaration __attribute__((used));

variable-definition __attribute__((used));

Remarks

This attribute specifies that the linker must not dead-strip a function or static variable even if

the linker determines that the rest of the program does not refer to the object.

AN3350 데이터시트(PDF) 117 Page - STMicroelectronics