The new C++ support involves new startup code that runs C++ initializers before main() is invoked. If you have a replacement for the file, crt0.o (or if you call main()), you must call __main() before calling main().
You may need to run these C++ initializers even if you do not write in C++ yourself. This could happen, for instance, if you are linking against a third-party library which itself was written in C++. You may not be able to tell that it was written in C++ because you are calling it with C entry points prototyped in a C header file. Without these initializers, functions written in C++ may malfunction.
If you are not using any third-party libraries, or are otherwise certain that you will not require any C++ constructors, you may suppress them by adding the following definition to your program.
int __main() {}
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