A preprocessor line of the form
# error token-sequenceopt
causes the preprocessor to write a diagnostic message that includes the token sequence.
C Programming
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A control line of the form
# pragma token-sequenceopt
causes the preprocessor to perform an implementation-dependent action. An unrecognized pragma is ignored.
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Several identifiers are predefined, and expand to produce special information. They, and also the preprocessor expansion operator defined, may not be undefined or redefined.
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__LINE__ |
A decimal constant containing the current source line number. |
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__FILE__ |
A string literal containing the name of the file being compiled. |
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__DATE__ |
A string literal containing the date of compilation, in the form “Mmmm dd yyyy” |
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__TIME__ |
A string literal containing the time of compilation, in the form “hh:mm:ss” |
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__STDC__ |
The constant 1. It is intended that this identifier be defined to be 1 only in standard-conforming implementations. |
#error and #pragma are new with the ANSI standard; the predefined preprocessor macros are new, but some of them have been available in some implementations
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