### warn_pch_portability

Controls whether or not to issue a warning when #pragma once on is used in a precompiled header.

##### Syntax

#pragma warn_pch_portability on | off | reset

##### Targets

All platforms.

##### Remarks

If you enable this pragma, the compiler issues a warning when you use #pragma once on in a precompiled header. This helps you avoid situations in which transferring a precompiled header from machine to machine causes the precompiled header to produce different results. For more information, see pragma once.

This pragma does not correspond to any panel setting. To check this setting, use __option (warn_pch_portability), described in Checking Settings. The default setting is off.