i960 Processor Compiler User's Guide
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• The predefined macro _ _STDC_ _ is not defined when you use
traditional, but _ _GNUC_ _ is (since the GNU extensions that
_ _GNUC_ _ indicates are not affected by traditional). When you
need to write header files that work differently depending on whether
traditional is in use, by testing both of these predefined macros
you can distinguish four situations: GNU C, traditional GNU C, other
ANSI C compilers, and other C compilers.
The following table summarizes the macros defined when the
traditional or ansi option is used.
_ _STRICT_ANSI_ __ _STDC_ __ _GNUC_ _
traditional X
ansi X X X
none X X
trigraphs (Trigraphs)
Support ANSI C
trigraphs.
Process ANSI standard trigraph sequences. These are three-character
sequences, all starting with
??, that are defined by ANSI C to stand for
single characters. For example,
??/ stands for \, so ’??/n’ is a character
constant for a newline.
The
ansi option also enables trigraphs.
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