26 lines
755 B
C
26 lines
755 B
C
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/* u_1_22.c: Undefined behaviors on generating invalid pp-token by ##
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operator. */
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#include <stdio.h>
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#define str( a) # a
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main( void)
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{
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/* u.1.22: Result of ## operator is not a valid pp-token. */
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#define NUM( dig, exp) dig ## E+ ## exp
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/*
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* "E+" is a sequence of two pp-tokens "E" and "+", not a single pp-token.
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* The first ## concatenates the last pp-token of first argument with "E",
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* and the second ## concatenates "+" with the first pp-token of the second
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* argument.
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* While "12E" (one of the sequence generated by the token concatenation)
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* is a valid pp-token, "+34" (the another sequence) is not a valid pp-token
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* and causes an undefined behavior.
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*/
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printf( "%e\n", NUM( 12, 34));
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return 0;
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}
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