Does C++ allow default return types for functions?

In C the following horror is valid:

  return 42;  // return type defaults to int.

But, what about in C++? I can't find a reference to it either way...

My compiler (Codegear C++Builder 2007) currently accepts it without warning, but I've had comments that this is an error in C++.


It's ill-formed in C++. Meaning that it doesn't compile with a standard conforming compiler. Paragraph 7.1.5/4 in Annex C of the Standard explains the change "Banning implicit int".

Implicit return types are valid in C89, but a lot of compilers warn about it.

They are not valid in C++, nor in C99.

So, it's definitely 'ill formed' C++, but it seems many compilers accept it with a warning at best.

  • Codegear C++Builder 2007: No error or warning at all
  • G++: Requires -W -Wall to generate warning , or -pedantic to generate error (Piotr)
  • MSVC 8: produces an error (tfinniga)
  • others...?

Please add to/correct this list!

This is not legal C++, but some compilers will accept it either silently or with a diagnostic.

As posted, it is ill-formed. MSVC 8 gives the following error:

error C4430: missing type specifier - int assumed. Note: C++ does not support default-int

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