VMS Help CC, Messages, MAINPROGEXT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Message        MAIN_PROGRAM is a language extension.

 Description    The use of MAIN_PROGRAM to designate a function as
                the main program is a language extension of Compaq C.
                Other C compilers might not successfully compile a
                program that uses the extension.

 User Action    The main program should be declared by naming the
                function main.