Control may reach end of non-void function error if-statement

Question

I\'m getting the error Control may reach end of non-void function on this code:

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInte         


        

Answer 1

While I agree with most answers that suggest to avoid multiple returns in the general, on occasions multiple returns is nice and useful. For instance dispatching on an enum:

#include 
#include 

enum direction { north, east, south, west };

std::string to_string(direction d)
{
  switch (d)
    {
#define CASE(C) case C: return #C
      CASE(north);
      CASE(east);
      CASE(south);
      CASE(west);
#undef CASE
    }
}

int main()
{
  std::cout << to_string(west) << '\n';
}

If you compile with GCC, you get (C or C++, it's the same):

$ g++-4.9 -Wall foo.cc
foo.cc: In function 'std::string to_string(direction)':
foo.cc:17:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^

Clang does not complain. Which is not so nice, actually, since it also compiles this without warnings:

int main()
{
  std::cout << to_string(direction(666)) << '\n';
}

which results in:

$ clang++-3.5 -Wall foo.cc
$ ./a.out
zsh: illegal hardware instruction  ./a.out

So one has to "fight" GCC's warning. One wrong approach would be to add say

default:  abort();

to the switch. Sure, it cures the symptom, but now GCC will no longer complain if I add a new direction, say zenith, but forget to cover it in to_string. So really, never use a default case when switching on an enum.

Then you can leave an abort after the switch (which is clumsy to do without using inner returns).