error C2275 : illegal use of this type as an expression

Question

When you name your source files *.c, MSVC assumes it's compiling C, which means C89. All block-local variables need to be declared at the beginning of the block.

Workarounds include:

• declaring/initializing all local variables at the beginning of a code block (directly after an opening brace {)
• rename the source files to *.cpp or equivalent and compile as C++.
• upgrading to VS 2013, which relaxes this restriction.

You might be using a version of C that doesn't allow variables to be declared in the middle of a block. C used to require that variables be declared at the top of a block, after the opening { and before executable statements.

Put braces around the code where the variable is used.

In your case that means:

if (ac > 1)
{
    if (!parse_args(ac, av))
    {
        aff_error(ARGUMENTS);
        return EXIT_FAILURE;
    }
}
{
    SERVICE_TABLE_ENTRY DispatchTable[] = {{MY_SERVICE_NAME, ServiceMain}, {NULL, NULL}};
    StartServiceCtrlDispatcher(DispatchTable);
}

This error occurred when transferring a project from one installation to another (VS2015 => VS2010).
The C code was actually compiled as C++ on the original machine, on the target machine the "Default" setting in Project Properties\C/C++\Advanced\Compile as was somehow pointing to C even though the source file was of type *.cpp.
In my small program, errors popped up regarding the placement in code of certain types e.g. HWND and HRESULT as well as on the different format of for loops , and C++ constructs like LPCTSTR, size_t, StringCbPrintf and BOOL. Comparison.
Changing the "Compile as" from Default to Compile as C++ Code (/TP) resolved it.