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According to MSVC manual (*1), cl.exe can skip including a header file when that: - contains #pragma once, or - starts with #ifndef, or - starts with #if ! defined. GCC has a similar trick (*2), but it acts more stricter (e. g. there must be _no tokens_ outside of #ifndef...#endif). Sun C lacked #pragma once for a looong time. Oracle Developer Studio 12.5 finally implemented it, but we cannot assume such recent version. This changeset modifies header files so that each of them include strictly one #ifndef...#endif. I believe this is the most portable way to trigger compiler optimizations. [Bug #16770] *1: https://docs.microsoft.com/en-us/cpp/preprocessor/once *2: https://gcc.gnu.org/onlinedocs/cppinternals/Guard-Macros.html
21 lines
540 B
C
21 lines
540 B
C
#ifndef _FILE_H_
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#define _FILE_H_
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/* This is file FILE.H */
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#include <fcntl.h>
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#ifndef L_SET
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# define L_SET 0 /* seek from beginning. */
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# define L_CURR 1 /* seek from current position. */
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# define L_INCR 1 /* ditto. */
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# define L_XTND 2 /* seek from end. */
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#endif
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#ifndef R_OK
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# define R_OK 4 /* test whether readable. */
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# define W_OK 2 /* test whether writable. */
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# define X_OK 1 /* test whether executable. */
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# define F_OK 0 /* test whether exist. */
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#endif
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#endif
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