C中的禁止内存位置(Off-limit memory locations in C)

 这段代码是否有效C： 
 
fputc(*("Checking 7 bytes before this string"-7), stdout);
 
 C标准中有什么反对这样做的吗？ 即在字符串文字之前读取几个字节。 那怎么样:(假设这些位置实际上存在于该过程中） 
 
for (i=(char *)0x400000; i<(char *)0x400800; ++i) fputc(*i, stdout);
 
 如果这些是有效的，C中是否有任何禁止存储位置？ 
 
 谢谢。 

Is this code valid C:
 
fputc(*("Checking 7 bytes before this string"-7), stdout);
 
Is there anything in the C standard against doing this? i.e reading a couple of bytes before a string literal. What about this: (assuming that these locations actually exist for the process)
 
for (i=(char *)0x400000; i<(char *)0x400800; ++i) fputc(*i, stdout);
 
If these are valid, are there any off-limit memory locations in C?
 
Thank you.

原文：https://stackoverflow.com/questions/9961732