Thread: assign a string to char pointer

do you have a question?

your last sprintf is wrong - it uses uninitialized pointer as destination buffer

should be

Code:

const char* str2;

...


str2 = str();

Except the function returns a const char*, so you should assign it to a const char*, and not a char*.
const char* is NOT a string, nor is char*. That is a lesson you must learn. They are pointers to char. Typically, in C, also a pointer to a number of chars. The difference is that one is const, the other is not.
And you should use a pointer to const, since you are returning a string literal, and they cannot be modified.

This is incorrect. A char pointer is not dynamic. You cannot work around the fact that you must have a static number of bytes in a buffer.
SourceForge.net: Common mistakes and errors - cpwiki

Originally Posted by fresh_girl

I know that we can use char pointer so we don't have to have static number of characters as in char name[25] here we can't enter more than 24 chars.
so, correct me if I'm wrong:
char * name;
cin>>name;//or cin.getline(name,25,'\n');
cout<<name;

That's C++. This is the C forum.

Originally Posted by Elysia

This is incorrect. A char pointer is not dynamic.

Sure it is.

Originally Posted by Elysia

You cannot work around the fact that you must have a static number of bytes in a buffer.

Sure I can.

Code:

#include<stdio.h>
#include<stdlib.h>

char * readline( void )
{
    int c = 0;
    size_t x = 0;
    char *s = realloc( NULL, x+1 );
    
    while( (c = fgetc(stdin)) != EOF && c != '\n' )
    {
        char *p = realloc( s, x+1 );
        if( p )
        {
            p[x++] = c;
            s = p;
        }
        else
            return "memory allocation failed";
    }
    s[x] = '\0';

    return s;
}

int main( void )
{
    char *line = NULL;
    
    printf("Type a line and hit enter: ");
    fflush(stdout);
    line = readline();
    
    printf("\'%s\'\n", line );

    return 0;
}

Now that's not you were talking about exactly, but it illustrates my point. Especially considering that they're actually using C++, in which case you could override the = operator (probably, haven't tried, don't actually care) to do what I've done.


Quzah.

Originally Posted by quzah

Sure it is.

No. The pointer doesn't itself is not any kind of dynamic storage.

Sure I can.

My point being that the buffer isn't truly dynamic. You cannot just put stuff in it and hope that it will accommodate all the data. It does not.
You can resize the buffer to accommodate all the data, however. But you still have a static number of bytes in the buffer.

I do get your point, though. To get an "unlimited" amount of storage in a buffer, you would use dynamic memory and expand on need.
However, reading directly into a char pointer is undefined behavior and was the point I was trying to make.