C++ string question

I've avoided C++ for a long time but after a few months of using two high level languages (PHP and Javascript), I can't productively rely on C's strings any more. So I have a question. Is there any way of using C's string's with old C functions like strcat() and strcpy(). Yeah, I'm aware of the C++ equivalents.


int main(void)
{
    string firstName = "John";
    string lastName = "Doe";
   
    //This doesn't compile.
    strcat(firstName, lastName.c_str());
    //This compiles but doesn't work.
    strcat(&firstName[0], lastName.c_str());
}

Note: I'm aware that firstName += lastName would work. Before migrating to C++ I have to find a way to get C++ strings to work with C functions. For example, in the Windows API there's a function called GetSystemDirectory(char * path, int size) which sets the variable 'path' with the path of the system directory. If possible I don't want to have to create C arrays to deal with functions like that. Thanks in advance.

>>1
Is there any way of using C's string's with old C functions
using *C++'s* strings with old C functions

Typo.

Have you tried firstName.c_str()?

Pro bono

>>3
Have you tried firstName.c_str()?
Yeah, that doesn't work either.

Is there any way of using C's string's with old C functions
you really shouldn't. c_str returns a const array and it shouldn't me modified.

why don't you use just char[]?

>c_str()
jeebooze that's some disgusting function name

>>6
why don't you use just char[]?
I'd like to avoid using char arrays if possible.

Is that really the only option. I guess I could use C arrays if I have to.

>>1
First of all, using strcat as an example makes you look borderline retarded, and on the wrong side of the border, at that.

Second, for functions like GetSystemDirectory .c_str() will work fine.

If you want to use functions which expect a buffer, you have two options. You can be a good boy and malloc or statically allocate a buffer which you then assign/return as an std::string.

Or you can depend on the way all existing implementations work, and on the wording of C++11 standard which kind of more or less seems to make this legal from now on, and do
buffer.resize(1024, '\0');
hr = GetFullPathName(path.c_str(), buffer.size(), &buffer[0], NULL);

Though I must add that if despite of your alleged C background you couldn't understand what's the problem with your code then you probably are not born to be a programmer and should consider a career in sucking dicks instead.

Forgot to add, then you should check the return value and if it's OK, shrink the buffer back to it.

>>8
I'd like to avoid using char arrays if possible.
I'd like to avoid using the functions designed to work on string, replacement for char arrays.
Are you an idiot?

Second, for functions like GetSystemDirectory .c_str() will work fine.


int main(void)
{
    string systemPath;
    GetSystemDirectory(systemPath.c_str(), systemPath.size());
}

This doesn't work. [code]c_str()[code] returns a [code]const char*[code]. Is there something I'm missing (aside from a brain?).

OP here, I used to be less inept with C before I whored myself with PHP.

>>9

#include <iostream>
#include <string>
using namespace std;

int main(void)
{
    string firstName = "John";
    string lastName = "Doe";
    firstName.resize(firstName.length() + lastName.length(), '\0');
    strcat(&firstName[0], lastName.c_str());
    cout << firstName;
    return 0;
}

Thank you for your solution.

Why not just work with string where you can, and just strcpy(my_char_array, my_cpp_string) wherever you need it in char * format?  It will be inefficient as fuck, but you get what you pay for when you don't have the balls to either stick with C or convert to C++ completely.

>>14
Woops, that should be strcpy(my_char_array, my_cpp_string.c_str()).

>>1
string SepplesGetSystemDirectory() {
     char buffer[MAX_PATH+1];
     GetSystemDirectory(buffer, MAX_PATH+1);
     return new string(buffer);
}

the

>>13
That is definitely non-standards compliant, because no C++ standard guarantees that the terminating zero is stored with the string, while strcat does write it. So you have to do
firstName.resize(firstName.length() + lastName.length() + 1, '\0');

int main(void)
{
    char * firstName = "John";
    char * lastName = "Doe";
  
    //This does compile.
    strcat(firstName, lastName);
    //This compiles and does work.
    strcat(&firstName[0], lastName);
}