How to use C++ data in asm with Intel syntax and compiling by gcc? [duplicate]

I have C++ code with asm input for working with string. How can I use them from main program in assembly?

#include <iostream>
#include <fstream>
#include <clocale>
#include <curses.h>

#define MAX_LENGTH 80

using namespace std;

void printWelcomeStr();

int main()
{
    char input_string[MAX_LENGTH];
    char output_string[MAX_LENGTH];
    cin.getline(input_string, MAX_LENGTH, '\n');
    asm
    (
        "lea eax, input_string\n""mov esi, %eax\n""lea eax, output_string\n""mov %edi, %eax\n""BEGINCYCLE:\n""lodsb\n""test al, al\n""je EXIT\n""cmp al, 41h\n" // >= 'A'"jnbe LatinLetterGeneral\n""jmp NEXT\n""LatinLetterGeneral:\n""cmp %al, 5Ah\n" // <= 'Z'"jnae LatinLetterFinal\n""cmp al, 61h\n" // >= 'a'"jnbe LatinLetterFinal\n""jmp NEXT\n""LatinLetterFinal:\n""cmp al, 7Ah\n" // > 'z'"ja NEXT\n""cmp ax, al\n""sub ax, 30h\n""push cx\n""mov cx, 2\n""rol dl, 4\n""mov ax, 300fh\n""and al,dl\n""aaa\n""aad 11h\n""pop cx\n""mov al, di\n""jmp NEXT\n""NEXT:\n""stosb\n""jmp BEGINCYCLE\n""EXIT:\n""stosb\n"
    );

    cout << "\n\nResult:"<< endl;
    ofstream file_output("output.txt");
    int i = 0;
    while (output_string[i] != '\0')
    {
        cout << output_string[i];
        file_output << output_string[i];
        i++;
    }
    cout << endl;
    file_output << endl;
    file_output.close();

    getch();
    system("pause");

    return 0;
}

I compile it with:

g++ -masm=intel -m32 -o main main.cpp

And get this errors:

/usr/bin/ld: /tmp/ccoToLty.o: in function `main':
main.cpp:(.text+0x110): undefined reference to `input_string'
/usr/bin/ld: lr4_comments.cpp:(.text+0x118): undefined reference to `output_string'
collect2: error: ld returned 1 exit status

Adding .intel_syntax noprefix doesn't help, only adds some more errors. What have I do it this way? Is it connect with some correct arrangement of "%" and "[]? What's totally correct way to use data from asm?