MS Detours - DetourAttach fails

Question

Feeling stupid here but why is this code giving me a syntax error in Visual Studio when trying to compile it?

    DetourAttach(&(PVOID&)true_create_file, create_file);

The compiler complains with (underlining the & after PVOID)

Error (active) E0018 expected a ')'

The code is literally copied from the Detours example page. I'm assuming it is because my containing file has a .c extension and is thus compiled as C by VS while the example has a .cpp extension and is compiled as C++.

I'm not entirely sure what's going on in this line with all the casting. Why doesn't the C compiler like it and how do I get it to compile this line?

Here's the complete listing of the code:

#include <Windows.h>
#include "detours.h"
#pragma comment(lib, "detours.lib")

static HANDLE(WINAPI *true_create_file) (LPCSTR file, DWORD access,
    DWORD share, LPSECURITY_ATTRIBUTES sec, DWORD disp, DWORD flags,
    HANDLE tmpl) = CreateFileA;

HANDLE WINAPI create_file(LPCSTR file, DWORD access, DWORD share,
    LPSECURITY_ATTRIBUTES sec, DWORD disp, DWORD flags, HANDLE tmpl) {
}

int hook_create_file() {
    DetourTransactionBegin();
    DetourUpdateThread(GetCurrentThread());
    /* syntax error */
    DetourAttach(&(PVOID&)true_create_file, create_file);
    DetourTransactionCommit();
}

PVOID is defined as

typedef void *PVOID;

it works thank you. can you explain why the code above would give a syntax error though? — user3700562, May 25 '19 at 16:21
If you want to use C++ and the C++ compiler, then either (1) rename your source file, or (2) add the command line option `/Tp` or `/TP`. Also see [/Tc, /Tp, /TC, /TP (Specify Source File Type)](https://learn.microsoft.com/en-us/cpp/build/reference/tc-tp-tc-tp-specify-source-file-type?view=vs-2019) on MSDN. — jww, May 26 '19 at 00:16

score 1 · Accepted Answer · answered May 27 '19 at 02:55

The &(PVOID&) part: cast the parameter to a reference to a pointer to void first, and then taking the address of that. As comment point out, you compile it as C, but the reference operation do not exist in C. So the compiler recognizes "&" as taking address, but only ")" behind it, then get the expected a ')' error.

Since PVOID& doesn't make sense here, just to increase readability. You could use PVOIDinstead of PVOID& here:

DetourAttach(&(PVOID)true_create_file, create_file);

You could also get the DetourAttach function details from here.

MS Detours - DetourAttach fails

1 Answers1