C++03 3.6.1.3: The function main shall not be used (3.2) within a program. ...
I wonder why this rule exists... Is anyone aware of any system/implementation where it would be a problem if main were used?
P.S. 1. I know the definition of the term used. 2. I know there are simple workarounds like calling a single MyMain() from main() and using MyMain() instead. 3. The question is about real-world implementations which would have a problem if the restriction weren't there. Thanks!
In addition to the other answers: The c++ spec guarantees that all static initialization has happened before main is called.
If code could call main then some static scoped object could call main, in which case a fundamental guarantee is violated.
The spec can't say "static scoped objects should not call main()" because many objects are not written specifically to be instantiated at static scope always. It also can't say that constructors should not call main() - because its very difficult to audit and prove that a constructor isn't calling a method, calling a method, that might sometimes, call main().