HELP! Getting a segmentation fault with this paRT OF MY CODE

[agirideep]

Write your question here.

template <typename T>
void Library<T>::generate()
{
   std::string author_names[] = {"James Wilson", "Thomas George", "Peter Lammens", "Matthew Marker" };
   
   std::vector<std::vector<std::string> > all_books = {
      {"Ready Ribbons", "Jumping Down", "Living In Life"},
      {"Just Shaved", "Ordering Dogs", "Partly Done"},
      {"Move Allowed", "No Way, No Play", "Kick Up"}
   };

   // Sets the books for each author.
   for (int i = 0; i < 3; ++i)
   {
      authors.push_back(Author<std::string>(author_names[i]));
      for (int i = 0; i < 3; ++i)
      {
         authors[i].set_book(all_books[i][j]);
      }
   }
}

[lastchance]

You probably meant to use j, not i, as the control index in the inner loop!

[Ganado]

If that compiles (as a segfault would imply), it means you have a global variable with the name 'j'.
I would nuke that code from orbit, personally.

Edit: Actually, it could just be a class-scope variable with the name 'j'. Still, really poor name for anything but a loop variable.

[seeplus]

all_books has a size 3 x 3 NOT 4 x 3 - hence seg fault when trying to access [3] as the last element is [2].

As you haven't provided working code that will compile, have a look at this:

#include <string>
#include <vector>
#include <iostream>

struct Author {
	std::string name;
	std::vector<std::string> books;

	Author(std::string n) : name(std::move(n)) {}

	void set_book(std::string book) {
		books.emplace_back(std::move(book));
	}

};

struct Library {
	void generate();
	std::vector<Author> authors;
};

void Library::generate() {
	const static std::string author_names[] { "James Wilson", "Thomas George", "Peter Lammens", "Matthew Marker" };

	const static std::vector<std::vector<std::string> > all_books {
	   {"Ready Ribbons", "Jumping Down", "Living In Life"}, // James Wilson
	   {"Just Shaved", "Ordering Dogs", "Partly Done"},  // Thomas George
	   {"Move Allowed", "No Way, No Play", "Kick Up"} // Peter Lammens
	   // No books for Matthew Marker!
	};

	// Sets the books for each author.
	authors.clear();
	for (size_t cnt {}; const auto& a : author_names)
		if (authors.emplace_back(a); cnt < all_books.size())
			for (const auto& b : all_books[cnt++])
				authors.back().set_book(b);
}

int main() {
	Library lib;

	lib.generate();

	for (const auto& l : lib.authors) {
		std::cout << l.name << '\n';

		for (const auto& b : l.books)
			std::cout << b << '\n';

		std::cout << '\n';
	}
}

which displays:

James Wilson
Ready Ribbons
Jumping Down
Living In Life

Thomas George
Just Shaved
Ordering Dogs
Partly Done

Peter Lammens
Move Allowed
No Way, No Play
Kick Up

Matthew Marker

[agirideep]

Thank you everyone