5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian KornbergerC preprocessor features:

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger

ee5342a8882c2fc7631fcffb5497e6597747887cTim Reddehase(1) The preprocessor is centered around the libpp.a library. This

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger library provides a tokenizing implementation of the preprocessing

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger stages of ANSI standard C. The same library is used to construct

ee5342a8882c2fc7631fcffb5497e6597747887cTim Reddehase a standalone prepreprocessor as well as a C compiler front end

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger that, compiled with the library, eliminates the need for a

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger separate preprocessing pass. Other C tools requiring C tokenizing

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger can use this library, providing a common interface to C language

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger tokens.

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger(2) The #pragma interface is exploited to allow the addition of new

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger directives and #pragma's without changing the preprocessor

ee5342a8882c2fc7631fcffb5497e6597747887cTim Reddehase executable. Most implementation details can be specified by

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger directives in the file "ppdefault.h" that is automatically included

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger (by the standalone cpp library wrapper) as an initialization step.

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger(3) #assert, #unassert and corresponding #if predicate tests have been

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger added to relieve the conflicts introduced by predefined #define

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger macros (e.g., unix, vax, u3b, ...). This is the same feature

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger present in the extended Reiser cpp that has been included in the

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger nmake distribution. (NOTE: #assert is a failed experiment)

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger(4) The implementation is sensitive to the incompatible differences

ee5342a8882c2fc7631fcffb5497e6597747887cTim Reddehase between the Reiser cpp (used by AT&T and BSD compilers) and the new

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger ANSI standard C. A compatibility dialect implements Reiser

ee5342a8882c2fc7631fcffb5497e6597747887cTim Reddehase features, allowing for a smooth transition to the ANSI standard.

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger

ee5342a8882c2fc7631fcffb5497e6597747887cTim Reddehase(5) To aid in the transition to ANSI, the preprocessor can do some

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger operations that would normally be done by the lexical analysis

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger stage of a compiler front end:

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger (a) convert new-style character constants to a form

ee5342a8882c2fc7631fcffb5497e6597747887cTim Reddehase recognized by all current compilers

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger

9020cdded5ce3a804bee9cee087702113629d87fIngo Becker (b) concatenate adjacent string literals

61308bbbb1cad998a0f7107ce4723471998dcd71Eugen Kuksa

9020cdded5ce3a804bee9cee087702113629d87fIngo Becker(6) The preprocessor can also warn about obsolete constructs used

9020cdded5ce3a804bee9cee087702113629d87fIngo Becker in the compatibility dialect and on non-standard constructs

9020cdded5ce3a804bee9cee087702113629d87fIngo Becker used in the ANSI dialect. The latter is useful in writing

5cad3e82e8c017bc189c4cecc00541ec19a2a6e2Julian Kornberger C code that is made to run through other implementations of

ee5342a8882c2fc7631fcffb5497e6597747887cTim Reddehase ANSI standard C.

9020cdded5ce3a804bee9cee087702113629d87fIngo Becker

(7) The preprocessor allows a C language implementor to take

advantage of local extensions without invalidating the

conformance of the C language implementation.

C9X additions:

(1) #pragma STDC ...

special forms always accecpted

(2) _Pragma unary operator for pragmas via macro expansion

_Pragma(string-literal)

#pragma a b c

_Pragma("a b c")

(3) keywords

restrict inline _Bool _Complex _Imaginary

(4) macros

__STDC_VERSION__ 199901L

__STDC_IEC_559__ 1 or undef

__STDC_IEC_559_COMPLEX__ 1 or udef

__STDC_ISO_10646__ yyyymmL

(5) empty arguments allowed in function-like macros

(6) variable arguments via ...

__VA_ARGS__ in replacement list only, expands to var args

only var args is ok (shall only appear in ...)

(7) hex floating constant with binary exponents

xxxxxx[pP]dddd

(8) // style comments

(9) universal characters, even in identifiers!

\uxxxx \Uxxxxxxxx

(10) LL ll ULL ull suffix for long long literals

(11) <stdarg.h> has va_copy()