不同的字符串初始化会产生不同的行为？ [英] Different string initialization yields different behavior?

问题描述

为什么当我使用下面的方法，将用于所有字符转换成字符串为大写，

 而（*后code）{
*后code = TOUPPER（*后code）;后code ++;
}
 

使用以下几种说法作品，

 字符错误[20];
的strcpy（错了，LA1 4yt）;
 

但下面没有，尽管他们是一样的吗？

 的char *错=LA1 4yt
 

在尝试我的程序崩溃写入非法地址（段错误，我presume）。它是与不是的malloc 荷兰国际集团的问题吗？没有空terimanted？它不应该是...

经过调试，我注意到它崩溃上的第一个字符指定为大写的尝试。

任何帮助AP preciated！

解决方案

 的char *错=LA1 4yt
 

该声明指向一个字符串常量。常量不能被修改，这就是为什么你的code崩溃。如果你写的更多的迂腐

 为const char *错=LA1 4yt //更好
 

那么编译器会赶上的错误。你或许应该这样做声明指向一个字符串，而不是创建一个数组的任何时间。

有二十个字符，以便写入空间此，在另一方面，器分配的读/写存储是细

 字符错误[20];
 

如果你想把它初始化字符串上面，你可以这样做，然后将被允许去改变它。

 字符错误[20] =LA1 4yt //可以修改
char的错误[] =LA1 4yt //可以修改;仅大到需要
 

How come when I use the following method, to be used to convert all the characters in a string to uppercase,

while (*postcode) {
	*postcode = toupper(*postcode);

	postcode++;
}

Using the following argument works,

char wrong[20];
strcpy(wrong, "la1 4yt");

But the following, doesn't, despite them being the same?

char* wrong = "la1 4yt";

My program crashes in an attempt to write to an illegal address (a segfault, I presume). Is it an issue with not mallocing? Not being null-terimanted? It shouldn't be...

Through debugging I notice it crashes on the attempt to assign the first character as its uppercase.

Any help appreciated!

解决方案

char* wrong = "la1 4yt";

This declares a pointer to a string constant. The constant cannot be modified, which is why your code crashes. If you wrote the more pedantic

const char* wrong = "la1 4yt"; // Better

then the compiler would catch the mistake. You should probably do this any time you declare a pointer to a string literal rather than creating an array.

This, on the other hand, allocates read/write storage for twenty characters so writing to the space is fine.

char wrong[20];

If you wanted to initialize it to the string above you could do so and then would be allowed to change it.

char wrong[20] = "la1 4yt"; // Can be modified
char wrong[]   = "la1 4yt"; // Can be modified; only as large as required

这篇关于不同的字符串初始化会产生不同的行为？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！