Compilation flags are parsed incorrectly unless the input files appears as the last argument

[petersohn]

If I have the following entry in compile_commands.json, everything works fine:

{
    "directory": "/home/peet/workspace/sokoban2/src",
    "command": "clang++ '-std=c++14' '-Wall' '-Wextra' '-Werror' '-ftemplate-backtrace-limit=0' '-I../src' '-I../cpp-util/include' '-c' '-o' 'AdvancedHeurCalculator.o' 'AdvancedHeurCalculator.cpp'",
    "file": "/home/peet/workspace/sokoban2/src/AdvancedHeurCalculator.cpp"
}

With no additional flags from ycm_jsondb_config.py, I have the following flags derived for this file:

['-std=c++14', '-Wall', '-Wextra', '-Werror', '-ftemplate-backtrace-limit=0', '-I/home/peet/workspace/sokoban2/src/../src', '-I/home/peet/workspace/sokoban2/src/../cpp-util/include', '-isystem', '/home/peet/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/../clang_includes']

However, if the input file name appears before the -o option, like this:

{
    "directory": "/home/peet/workspace/sokoban2/src",
    "command": "clang++ '-std=c++14' '-Wall' '-Wextra' '-Werror' '-ftemplate-backtrace-limit=0' '-I../src' '-I../cpp-util/include' '-c' 'AdvancedHeurCalculator.cpp' '-o' 'AdvancedHeurCalculator.o'",
    "file": "/home/peet/workspace/sokoban2/src/AdvancedHeurCalculator.cpp"
}

Then the flags are derived wrong and YCM doesn't work. The flags derived in this case are the following:

['-std=c++14', '-Wall', '-Wextra', '-Werror', '-ftemplate-backtrace-limit=0', '-I/home/peet/workspace/sokoban2/src/../src', '-I/home/peet/workspace/sokoban2/src/../cpp-util/include', 'AdvancedHeurCalculator.cpp', '-isystem', '/home/peet/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/../clang_includes']

If I try to use the YCM features, it simply won't work.