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Pointer to char array C ++

I have a problem converting the following code from c to C ++:
I have a function that accepts an array of move sequences (a sequence of characters from a to i) as arg.

code:

void mkmove(char** move) {
    int i = 0;
    char* p = NULL;
    int moves[9][9];

    for(int i = 0; i < 9; i++) {
        for(p = move[i]; *p; p++) {
            moves[i][*p - 'a'] = 3;
        }
    }
}

int main() {
    char* movestr[] = {"abde", "abc", "bcef", "adg", "bdefh", "cfi", "degh", "ghi", "efhi"};
    mkmove(movestr);

    return(0);
}

gcc compiles this code ok, but if I try to compile it with g ++ it gives the following warning:
main.cpp: 17: 39: warning: deprecated conversion from string constant to 'char * [-Wwrite-strings]

I believe this warning comes from the fact that a string in C is defined as char [], and C ++ uses std :: string.
So I tried to replace the code using C ++ strings like this:

void mkmove(std::string* move) {

in the mkmove defenition function and:

std::string* movestr = {'abde', "abc", "bcef", "adg", "bdefh", "cfi", "degh", "ghi", "efhi"};

in your main function and add the C ++ line header file:

#include <string>

but now I get errors:
main.cpp: In function 'void mkmove (std :: string *):
main.cpp: 11: 21: error: cannot convert' std :: string {aka std :: basic_string} to 'char * in the task
main.cpp: In the function 'int main ():
main.cpp: 19: 39: error: scalar object' movestr requires one element in the initializer

I tried some other settings as well, but that gave me fewer compilation errors.

So what is the correct way to convert the top code from C to C ++?

Thanks for answers!

-Slovenia1337

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3 answers


using



std::string movestr[] = {"abde", "abc", "bcef", "adg", "bdefh", "cfi", "degh", "ghi", "efhi"};
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No, the warning is not because you should use string

, because character strings are read-only.

Either declare strings like char ...[]

or like const char *

.



In your case, you are declaring an array char *

, which is a deprecated function (converting from const char *

to char *

.

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I believe this warning comes from the fact that a string in C is defined as char[]

, whereas C ++ uses std::string

.

No, C string literals have a constant char[]

, while C ++ has a const char[]

.

Correct the const-correctness of your program like this:

void mkmove(const char** move) {
    const char* p;
    int moves[9][9];

    for(int i = 0; i < 9; i++) {
        for(p = move[i]; *p; p++) {
            moves[i][*p - 'a'] = 3;
        }
    }
}

int main() {
    const char* movestr[] = {"abde", "abc", "bcef", "adg", "bdefh", "cfi", "degh", "ghi", "efhi"};
    mkmove(movestr);

    return(0);
}
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