返回一个指向文字（或常量）字符数组（字符串）的指针？

Question

I know this is wrong:

char* getSomething() {  
    char szLocal[5];  
    /* put something in the char array somehow */  
    return szLocal;  
}  

...because szLocal can be destroyed sometime after the function returns.

But is this ok?

char* getSomethingElse() {  
    return "something else";  
}  

Answer 1

That is actually OK. The string literal is usually allocated in an immutable memory area that remains available for as long as your program is running.

See also the answers to when does c/c++ allocate string literals .

Answer 2

It's ok in terms of allocation: the string literal is implicitly static . It's not ok to return a non- const pointer to a literal.

If you want to return a modifiable (non- const ) string, declare it a static char[] . Or better, return a copy:

return strdup("something else");

Don't forget to free afterwards. strdup is non-ISO but available almost everywhere (except MSVC, I believe).

Answer 3

The type of a string literal is const char * (see comments below) static char[] , but immutable. A string literal represents a pointer to statically allocated memory. Therefore:

1. It is perfectly fine, to return a such a pointer.

2. Your function return type must should be compatible with const char* , ie, return type char * will give you at least a warning may give you trouble later on.

3. If you function may return both a literal or malloc ed string you have to be very careful about memory management. free ing a string literal probably will segfault.