Send struct with char[] in MPI - c++

Question

I'm trying to send some data from workers to a master (ranked 0) in a MPI program in C++. The goal is to pass 2 strings and an integer. To do that, I've created a struct.
The struct
It is called word and defined as follows:
struct word
{
char word_name[str_size];
char url[str_size];
int counter;
};
/* Some important variables to the question */
MPI_Datatype mpi_word_type;
const int str_size = 200;
Previously I was trying this through char * but it doesn't work, since the processes don't share the same memory space.
By now, I'm able to send the struct if I change the variables from char[] to a simple char and try with an example. With this as it is above, I cannot get rid of Segmentation fault errors.
Sending Part - Workers
I start by creating and filling an example struct and then sending the size of the struct first and the struct itself, secondly. Like this:
word word_col;
std::string tmp = "somename";
strcpy(word_col.word_name, tmp.c_str());
std::string tmp2 = "someurl";
strcpy(word_col.url, tmp2.c_str());
word_col.counter = 10;
int size = sizeof(word_col);
MPI::COMM_WORLD.Send(&size, 1, MPI::INT, 0, 1);
MPI::COMM_WORLD.Send(&word_col, size, mpi_word_type, 0, 1);
Receiving Part - Master
const int nitems = 3;
int blocklengths[3] = { str_size, str_size, 1 };
MPI_Datatype types[3] = { MPI::CHAR, MPI::CHAR, MPI::INT };
MPI_Aint offsets[3];
offsets[0] = (MPI_Aint) offsetof(struct word, word_name);
offsets[1] = (MPI_Aint) offsetof(struct word, url);
offsets[2] = (MPI_Aint) offsetof(struct word, counter);
MPI_Type_create_struct(nitems, blocklengths, offsets, types, &mpi_word_type);
MPI_Type_commit(&mpi_word_type);
...
for(...)
{
word word_col;
int size;
MPI::COMM_WORLD.Recv(&size, 1, MPI::INT, MPI::ANY_TAG, 1, status);
MPI::COMM_WORLD.Recv(&word_col, size, mpi_word_type, MPI::ANY_TAG, 1, status);
}
I've been struggling with this for hours and I've seen many examples and another questions about this, but I couldn't figure out what is the problem here.

Answer 1

This is erroneous programming. You have unallocated and uninitialized pointer and you are trying to push data to that.
You have two options:
Either you define your structure as:
const int str_size = 200;
struct word
{
char word_name[str_size]; // fixed sized char array
char url[str_size]; // fixed sized char array
int counter;
};
Or,
const int str_size = 200;
struct word
{
char *word_name; /
char *url;
int counter;
Word() {
word_name = new char[str_size];
url = new char[str_size];
}
~Word() {
delete [] word_name;
delete [] url;
}
};
The idea is that you need to have allocated memory for these variables
Also, while receiving, you have used:
MPI::COMM_WORLD.Recv(&word_col, size, mpi_word_type, MPI::ANY_TAG, 1, status);
Shouldn't it be like below?
MPI::COMM_WORLD.Recv(&word_col, sizeof(word_col), mpi_word_type, MPI::ANY_TAG, 1, status);