struct initialization failure

I'm having difficulty initializing a struct in code per below. Can this even be done, or do I 开发者_开发问答really need to memcpy (urg) the 5-character string into the struct?

struct MyStruct  
{  
    char x[5];  
};

main(...)  
{  
    const char* MyString = {"mnopq"}; // I understand this is a non-NULL terminated string -  
                                  // it's OK, I just want five character fields in an array

struct MyStruct = {MyString};     // <---This gives warnings below  
}

warning: missing braces around initializer

warning: initialization makes integer from pointer without cast

If I wrap initializer like:

struct MyStruct = {{MyString}};

the first warning goes away. The second warning does not. And, thus, the struct is not initialized as hoped.

Thanks in advance for help.

"mnopq" is an array, const char * MyString is not.

struct MyStruct foo = {"abcde"}; will work, whereas your approach converts the pointer MyString to an integral value and assigns it to the first element of x.

You are trying to fill a char array with a pointer. MyString is seen as a const char * instead of an array. Change your type in the structure to const char *x, and it should do the trick. Also, MyString is actually a NULL terminated string here. The compiler sets it into memory with the extra NULL byte at the end, then treats MyString like a const char *.

If you do want the char x[5] instead of the const char *, you could initialize in a couple of ways,

struct MyStruct ms = {{'m', 'n', 'o', 'p', 'q'}};

or you could do

struct MyStruct ms = {{ MyString[0], MyString[1], MyString[2], MyString[3], MyString[4]}};

The first set of braces is for initializing the struct members, the second set is for initializing the char array members, so each member(char) has to be set individually.

You need to declare a variable of the type MyStruct and assign it's x value to that string. This should work:

struct MyStruct {
char x[5];
};

int main(int argc, char *argv[]) {

   struct MyStruct a;
   const char* MyString = "mnop";

   strncpy((a.x), MyString, 5);

   /* 
    *if within the 5 characters you do not have the null char it will 
    * also print garbage
    */
   printf("%s", a.x);

   return 0;
}

However you can't assign a pointer to const char to an array of char as they are different types. So you would need to either use char* in the struct or use memcpy / strcpy to get the information.

The answer by DavidMFrey is correct and should get credit before mine! However, here's the source code using his answer as I was able to run it:

#include <stdio.h>
struct MyStruct  
{  
    char x[5];  
};
int main(void)  
{  
    const char* MyString = "mnopq";
    struct MyStruct foo = {{ MyString[0], MyString[1], MyString[2], MyString[3], MyString[4]}};
    printf("foo.x is: %s\n", foo.x); // outputs: foo.x is: mnopq¦ah¦"

    struct MyStruct ms = {{'m', 'n', 'o', 'p', 'q'}};
    printf("ms.x is: %s\n", ms.x);   // ms.x is: mnopq

    return 0;
}