This pragma enables the compiler to skips subsequent includes of that header file.
#pragma once is accepted for compatibility
with other compilers, and enables you to use other forms of header
guard coding. However, it is preferable to use #ifndef and #define coding because
this is more portable.
ExampleThe following example shows the placement of a #ifndef guard
around the body of the file, with a #define of
the guard variable after the #ifndef.
#ifndef FILE_H
#define FILE_H
#pragma once // optional ... body of the header file ...#endif
The #pragma once is marked as optional
in this example. This is because the compiler recognizes the #ifndef header
guard coding and skips subsequent includes even if #pragma
once is absent.
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