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Asked: 2026-05-11T18:25:33+00:00

I was looking at the program at http://www0.us.ioccc.org/1988/westley.c , mentioned in another SO answer

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I was looking at the program at http://www0.us.ioccc.org/1988/westley.c, mentioned in another SO answer – it’s supposed to print the value of pi, about 3.142, but when I compile it and run it I get 0.250. It looks like when the GCC preprocessor (both 4.1.2 and 3.4.6 tested) runs on the code, it converts 

#define _ -F<00||--F-OO--;
_-_-_

to

-F<00||--F-OO--;- -F<00||--F-OO--;- -F<00||--F-OO--;

but I think, for the program to work, it should be

-F<00||--F-OO--;--F<00||--F-OO--;--F<00||--F-OO--;

i.e. GCC is inserting an extra space before the “macro” expansion. Is that the way #define is supposed to work? (Has that changed since 1988?)

EDIT: Also, any information about how to prevent those spaces from showing up would be appreciated.

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1 Answer

  1. Editorial Team

    The preprocessor operates on tokens, not strictly text. So technically it doesn’t “put a space” in between, but unless you explicitly tell it to paste two tokens together with the ## operator, it won’t do it. In this case the two -‘s across macro lines are counted as two different tokens – both meaning unary minus, not decrement.

    see also: http://en.wikipedia.org/wiki/C_preprocessor#Token_concatenation

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