Error: "invalid operands to Binary Expression ('char *' and 'char *')"

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3

I need to create a string which contains "Mr: n" and the name of the person concerned (pessoa->nome).

char* endereca(Pessoa* pessoa)
{
    if(pessoa->sexo == 'M')
    {
        char *msg;
        msg = (char*)malloc(7*sizeof(char) + sizeof(pessoa->nome));

        msg = "Ao Sr.:\n" + pessoa->nome; //Erro aqui
    }
}
c allocation string-concatenation

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2 answers

3

In C to concatenate strings it is necessary to use the function strcat(). So it would look something like this:

char* endereca(Pessoa* pessoa) {
    if (pessoa->sexo == 'M')  {
        char *msg = malloc(8 + sizeof(pessoa->nome));
        msg = strcat("Ao Sr.:\n", pessoa->nome);
    }
}

I put in the Github for future reference.

I put 8 because the string You need space for your null terminator. If you have any chance of this changing it would be better not to leave this constant size but to check the size of the string with sizeof. I took the sizeof of char because it always is 1. I took the cast because he doesn’t do something useful, on the contrary.

2

You’re trying to put two pointers together

msg = "Ao Sr.:\n" + pessoa->nome;

This is an operation that doesn’t exist in C.

What you’re probably trying to do is this:

static const char saudacoes[] = "Ao Sr.:\n";
char* msg = malloc(sizeof(saudacoes) + strlen(pessoa->nome));
strcpy(msg, saudacoes);
strcat(msg, pessoa->nome);

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