在字符常量多个字符 [英] Multiple characters in a character constant

问题描述

一些C编译器允许在字符常量多个字符。
  这意味着，写作，而不是是是很可能不被发现。
  资料来源：C陷阱和缺陷

Some C compilers permit multiple characters in a character constant. This means that writing 'yes' instead of "yes" may well go undetected. Source: C traps and pitfalls

谁能给在多个字符允许的字符常量这样的例子？

Can anyone give an example of this where multiple characters are allowed in a character constant?

推荐答案

由于code猴引，这是实现定义和实现不同 - 它不只是一个大尾端/ LittleEndian和字符集的区别。我与程序测试4实现（全部采用ASCII）

As Code Monkey cited, it is implementation defined and implementation varies -- it isn't just a BigEndian/LittleEndian and charset difference. I've tested four implementations (all using ASCII) with the program

#include <stdio.h>

int main()
{
    unsigned value = 'ABCD';
    char* ptr = (char*)&value;

    printf("'ABCD' = %02x%02x%02x%02x = %08x\n", ptr[0], ptr[1], ptr[2], ptr[3], value);
    value = 'ABC';
    printf("'ABC'  = %02x%02x%02x%02x = %08x\n", ptr[0], ptr[1], ptr[2], ptr[3], value);
    return 0;
}

和我有四个不同的结果。

and I got four different results

大端（AIX，POWER，IBM编译器）

Big endian (AIX, POWER, IBM compiler)

'ABCD' = 41424344 = 41424344
'ABC'  = 00414243 = 00414243

大端（Solaris和SPARC上，Sun编译）

Big endian (Solaris, Sparc, SUN compiler)

'ABCD' = 44434241 = 44434241
'ABC'  = 00434241 = 00434241

小尾数（Linux操作系统，x86_64的，GCC）

Little endian (Linux, x86_64, gcc)

'ABCD' = 44434241 = 41424344
'ABC'  = 43424100 = 00414243

小尾数（Solaris中，x86_64的，Sun编译）

Little endian (Solaris, x86_64, Sun compiler)

'ABCD' = 41424344 = 44434241
'ABC'  = 41424300 = 00434241

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