Undefined symbol main (referred from rtentry2.o

I think you are probably missing a C file in your project. With the same name as the .o file.
The compiler is supposed to compile a C file to a object file. And the linker is supposed to
use the .o file with the same base name as the C file. Maybe I did not explained 100 percent
correct. From the errors that I have had if I add the C file to the project and that type of error will go away.

I think you are probably missing a C file in your project. With the same name as the .o file.
The compiler is supposed to compile a C file to a object file. And the linker is supposed to
use the .o file with the same base name as the C file. Maybe I did not explained 100 percent
correct. From the errors that I have had if I add the C file to the project and that type of error will go away.

Sorry, got off track. But searched and saw a discussion where the main.c file was left out of the project.

http://www.keil.com/forum/18753/

http://www.keil.com/forum/20539/

So - is this an assembler-only project or a C/C++ project?'

If it's a C/C++ project, then you should have an object file containing a function named _main() - so you should have compiled a source file with a main(). Did you? Is it part of the build?