AN3350 datasheet(160/185 Pages) STMICROELECTRONICS

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Pragmas for preprocessing

AN3350

160/185

Doc ID 018512 Rev 2

20.11

notonce

Controls whether or not the compiler lets included files be repeatedly included, even with

#pragma once on

Syntax

#pragma notonce

Remarks

If you enable this pragma, files can be repeatedly #included, even if you have enabled

#pragma once on

. For more information, see once.

20.12

old_pragma_once

This pragma is no longer available.

20.13

once

Controls whether or not a header file can be included more than once in the same

compilation unit.

Syntax

#pragma once [ on ]

Remarks

Use this pragma to ensure that the compiler includes header files only once in a source file.

This pragma is especially useful in precompiled header files.

There are two versions of this pragma:

#pragma once

and

#pragma once on

Use #pragma once in a header file to ensure that the header file is included only once in a

source file. Use #pragma once on in a header file or source file to ensure that any file is

included only once in a source file.

Beware that when using #pragma once on, precompiled headers transferred from one

host machine to another might not give the same results during compilation. This

inconsistency is because the compiler stores the full paths of included files to distinguish

between two distinct files that have identical file names but different paths. Use the

warn_pch_portability

pragma to issue a warning message when you use #pragma

once on

in a precompiled header.

Also, if you enable the old_pragma_once on pragma, the once pragma completely

ignores path names.

This pragma does not correspond to any panel setting. By default, this pragma is off.

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