37 lines
1.3 KiB
C
37 lines
1.3 KiB
C
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/*
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* unspcs.c:
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* 1998/08 made public kmatsui
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*
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* These texts are unportable ones, because the order of the evaluation is
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* unspecified. Good preprocessor will warn at these texts even if the
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* results are valid. Good preprocessor will also document the order of
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* evaluation and the behavior on invalid results.
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* Note: Order of evaluation of sub-expressions (other than operands of &&,
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* ||, ? :) of #if expression is also unspecified. The order, however, never
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* affects the result, because #if expression never cause side effect, so no
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* warning is necessary. Precedence and grouping rules of operators are other
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* things than order of evaluation, and shall be obeyed by preprocessor.
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*/
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#include "defs.h"
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#define str( a) # a
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#define xstr( a) str( a)
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main( void)
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{
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/* s.1.1: Order of evaluation of #, ## operators. */
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#define MAKWIDESTR( s) L ## # s
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/* Either of L"name"; or L# name; ("L#" is not a valid pp-token). */
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assert( MAKWIDESTR( name)[ 0] == L'n');
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/* s.1.2: Order of evaluation of ## operators. */
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#define glue3( a, b, c) a ## b ## c
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/* "1.a" or undefined, since .a is not a valid pp-token, while 1. and 1.a are
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valid pp-tokens. */
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puts( xstr( glue3( 1, ., a)));
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return 0;
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}
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