Is #pragma once a Reliable Cross-Platform Include Guard?

Concerns over Platform Compatibility of #pragma once Include Guard

Question:

Can #pragma once be used as a reliable include guard without introducing cross-platform compatibility issues, particularly when targeting non-Windows platforms?

Details:

Some compilers optimize compilation when using #pragma once, potentially improving speed. However, cross-platform compatibility could be compromised as it is a non-standard directive.

Answer:

While #pragma once can indeed enhance compilation speed, it comes with a significant drawback:

#pragma once Drawback:

If the same file exists in multiple locations (e.g., due to build system file copying), the compiler interprets these instances as unique files when they are not. This can lead to unexpected compilation errors.

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