[FIX] Fix return value of main() if program failed

[knst]

If *.cpp2 file contains any syntax error or in case if wrong arguments are specified, the cppfront will return success (main returns 0).

This patch propagates error code as a result of cppfront in case of wrong arguments or in case of syntax error in at least one input file.

It may allow to write scripts that runs build of resulting C++ output or any other steps such as [example for Bash]:
cppfront main.cpp && echo OK

[hsutter]

Thanks -- this seems useful, but -1 and -2 seem to be nonportable values... should it just be EXIT_FAILURE?

The C and C++ standards talk about 0, EXIT_FAILURE, or EXIT_SUCCESS, which are implementation-defined but a quick Godbolt test shows they appear to often be 0 and 1 respectively on the major compilers on at least the OSes being used here: https://godbolt.org/z/EchfErqYs

You can also return from main, or call exit, with your own value but it may be translated... See: https://en.cppreference.com/w/c/program/exit. Pasting related sample doc material from cppreference since I have them open:

If exit_code is 0 or EXIT_SUCCESS, an implementation-defined status indicating successful termination is returned. If exit_code is EXIT_FAILURE, an implementation-defined status indicating unsuccessful termination is returned. In other cases implementation-defined status value is returned.

Both EXIT_SUCCESS and the value zero indicate successful program execution status (see std::exit), although it is not required that EXIT_SUCCESS equals zero.

See this Godbolt example for exit(-2) and return -2;... https://godbolt.org/z/f66zPKnjW

• MSVC on Windows: MSVC generates mov eax, 0xfffffffe, the OS reports Program returned: 4294967294
• Gcc and Clang: Compilers both generate mov eax, -2, the OS reports Program returned: 254

So perhaps just return EXIT_FAILURE on failure... thanks!

[filipsajdak]

I have used EXIT_SUCCESS and EXIT_FAILURE as it is described on cppreference.

[wingunder]

To be complete, change line 2668 to return EXIT_SUCCESS;

[hsutter]

Looks good, thanks!