Question

Turns out that g++ compiler (used in Qt Creator by default) gives a mere warning if you don’t have return statement in the non-void function, i.e.:

int* create_array(int n)
{
    int* a = new int[n];
}

compiles fine.

This behavior is subject to countless bug reports on g++ itself, but looks like developers consider this behavior conforming to C++ standard (which is debatable, cause it’s a bit confusing in this part) as stated at http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43943 :

Flowing off the end of a function is equivalent to a return with no value; 
this results in undefined behavior in a value-returning function.

However, the very same paragraph begins with:

  A return statement without an expression can be used only in functions 
  that do not return a value, that is, a function with the return type void,
  a constructor (12.1), or a destructor (12.4).

So aside from these (un)holy wars over the standard interpretation are there any options to make Qt flag this as an error at compile time?

Answer 1

This is not related to Qt but to g++.

In the build options, simply add the flag -Werror and g++ will consider any warning as error. You may also need to use flag -Wall to make g++ generate additional warnings, as it doesn’t generate warnings for missing return statements (and many other situations) by default. There’s no way to tune this setting on a per-warning basis however, so it’s either everything or nothing.