c – 多字符恒定警告

[weixin_38068653]

为什么这是一个警告？我认为在很多情况下使用multi-char int常量而不是“无意义”数字或者使用相同值定义const变量更为明确.解析wave / tiff /其他文件类型时,可以更清楚地将读取值与某些“EVAW”,“数据”等进行比较,而不是相应的值. 示例代码： int waveHeader = 'EVAW'; 为什么这会发出警告？

[weixin_38069804]

According to the standard(§6.4.4.4/ 10) The value of an integer character constant containing more than one character (e.g., ‘ab’), […] is implementation-defined. long x = '\xde\xad\xbe\xef'; // yes, single quotes 这是有效的ISO 9899：2011 C.它在没有警告的情况下使用-Wall编译gcc,并且使用-pedallic编译“多字符字符常量”警告. 从Wikipedia开始： Multi-character constants (e.g. ‘xy’) are valid, although rarely useful — they let one store several characters in an integer (e.g. 4 ASCII characters can fit in a 32-bit integer, 8 in a 64-bit one). Since the order in which the characters are packed into one int is not specified, portable use of multi-character constants is difficult. 为了便于携带,请不要使用带有整数类型的多字符常量.