gcc-you can use this code to learn something about gcc, and inquire further into linux,
源代码在线查看： if-paren.c
/* Copyright (C) 2000 Free Software Foundation, Inc. */ /* { dg-do preprocess } */ /* These now use "!=" rather than " #if 16 * (1) + 4 != 20 #error /* { dg-bogus "error" "with paren" } */ #endif #if 16 * 1 + 4 != 20 #error /* { dg-bogus "error" "without paren" } */ #endif #if () /* { dg-error "expression between" "empty paren" } */ #endif #if (1) == 1 #error /* { dg-error "error" "simple parens no. 1" } */ #endif #if (2) #error /* { dg-error "error" "simple parens no. 2" } */ #endif #if 3 == (3) #error /* { dg-error "error" "simple parens no. 3" } */ #endif #if (((-1) + 8)) == ((+2) * ((3)) - -1) #error /* { dg-error "error" "nested parentheses" } */ #endif
