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