3.6.1 Main function [basic.start.main]
1 A program shall contain a global function called main, which is the designated start of the program. It is
implementation-defined whether a program in a freestanding environment is required to define a main
function. [Note: in a freestanding environment, start-up and termination is implementation-defined; startup
contains the execution of constructors for objects of namespace scope with static storage duration; termination
contains the execution of destructors for objects with static storage duration. ]
2 An implementation shall not predefine the main function. This function shall not be overloaded. It shall
have a return type of type int, but otherwise its type is implementation-defined. All implementations
shall allow both of the following definitions of main:
int main() { /* ... */ }
and
int main(int argc, char* argv[]) { /* ... */ }
In the latter form argc shall be the number of arguments passed to the program from the environment in
which the program is run. If argc is nonzero these arguments shall be supplied in argv[0] through
argv[argc-1] as pointers to the initial characters of null-terminated multibyte strings (NTMBSs)
(17.3.2.1.3.2) and argv[0] shall be the pointer to the initial character of a NTMBS that represents the
name used to invoke the program or "". The value of argc shall be nonnegative. The value of
argv[argc] shall be 0. [Note: it is recommended that any further (optional) parameters be added after
argv. ]
3 The function main shall not be used (3.2) within a program. The linkage (3.5) of main is
implementation-defined. A program that declares main to be inline or static is ill-formed. The
name main is not otherwise reserved. [Example: member functions, classes, and enumerations can be
called main, as can entities in other namespaces. ]
4 Calling the function
void exit(int);
declared in <cstdlib> (18.3) terminates the program without leaving the current block and hence without
destroying any objects with automatic storage duration (12.4). If exit is called to end a program during
the destruction of an object with static storage duration, the program has undefined behavior.
5 A return statement in main has the effect of leaving the main function (destroying any objects with automatic
storage duration) and calling exit with the return value as the argument. If control reaches the end
of main without encountering a return statement, the effect is that of executing
return 0;
