gcc-you can use this code to learn something about gcc, and inquire further into linux,
源代码在线查看： if-unary.c
/* Copyright (C) 2000 Free Software Foundation, Inc. */ /* { dg-do preprocess } */ /* Test the various unary operators. */ #if 1 + + + 1 /* allow multiple unary sign operators :) */ #endif #if 8 - +3 != +4 + +1 #error /* { dg-bogus "error" "unary +" } */ #endif #if -2 - -1 != -1 #error /* { dg-bogus "error" "unary -" } */ #endif #if ~0 != -1 #error /* { dg-bogus "error" "unary ~" } */ #endif #if !0 && (!1 == 0) && !!1 != 1 #error /* { dg-bogus "error" "unary !" } */ #endif #if ~~8 != 8 #error /* { dg-bogus "error" "double unary ~" } */ #endif #if 5 + +!-4 != 5 #error /* { dg-bogus "error" "compound unary +, !, -" } */ #endif
