error C2275 : illegal use of this type as an expression

Question

Since yesterday, I've been facing a compiling error for my C project. The project itself consists on creating a service that will make some tasks.

I don't what has changed since yesterday, but this morning, my code can't compile anymore.

Here are the errors I have :

c:\path\main.c(56): error C2275: 'SERVICE_TABLE_ENTRY' : illegal use of this type as an expression
c:\program files\microsoft sdks\windows\v7.0a\include\winsvc.h(773) : see declaration of 'SERVICE_TABLE_ENTRY'
c:\path\main.c(56): error C2146: syntax error : missing ';' before identifier 'DispatchTable'
c:\path\main.c(56): error C2065: 'DispatchTable' : undeclared identifier
c:\path\main.c(56): error C2059: syntax error : ']'
c:\path\main.c(57): error C2065: 'DispatchTable' : undeclared identifier
c:\path\main.c(57): warning C4047: 'function' : 'const SERVICE_TABLE_ENTRYA *' differs in levels of indirection from 'int'
c:\path\main.c(57): warning C4024: 'StartServiceCtrlDispatcherA' : different types for formal and actual parameter 1

Here's the code concerned by these errors (from lines 45 to 58) :

int main(int ac, char *av[])
{
    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);
    return EXIT_SUCCESS;
}

And here's the code of my ServiceMain function :

void WINAPI ServiceMain(DWORD ac, LPTSTR *av)
{
    gl_ServiceStatus.dwServiceType = SERVICE_WIN32;
    gl_ServiceStatus.dwCurrentState = SERVICE_START_PENDING;
    gl_ServiceStatus.dwControlsAccepted = SERVICE_ACCEPT_STOP;
    gl_ServiceStatus.dwWin32ExitCode = 0;
    gl_ServiceStatus.dwServiceSpecificExitCode = 0;
    gl_ServiceStatus.dwCheckPoint = 0;
    gl_ServiceStatus.dwWaitHint = 0;
    gl_ServiceStatusHandle = RegisterServiceCtrlHandler(MY_SERVICE_NAME, ServiceCtrlHandler);
    if (gl_ServiceStatusHandle == (SERVICE_STATUS_HANDLE)0)
        return;
    gl_ServiceStatus.dwCurrentState = SERVICE_RUNNING;
    gl_ServiceStatus.dwCheckPoint = 0;
    gl_ServiceStatus.dwWaitHint = 0;
    SetServiceStatus(gl_ServiceStatusHandle, &gl_ServiceStatus);
}

I couldn't manage to find some answers that fit my problem, could anyone helps ? Thanks !

Solution 1

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.

Solution 2

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.

Solution 3

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);
}

Solution 4

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.

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