one symbol found and for other "unresolved external symbol"

Question

In my Visual Studio 2010 there are 2 projects. One is a static lib (mhook 2.3 if someone asks) and the other is a DLL. Both are set to compile as /MT.

mhook project has two functions in its mhook.h:

BOOL Mhook_SetHook(PVOID *ppSystemFunction, PVOID pHookFunction);
BOOL Mhook_Unhook(PVOID *ppHookedFunction);

the dll project references the mhook project and uses both Mhook_SetHook and Mhook_Unhook. Same mhook.h is used. When I compile the dll project, I get the following error:

1>hookdll.obj : error LNK2001: unresolved external symbol _Mhook_Unhook

Note, that the linked successfully found the Mhook_SetHook. If I comment out the use of Mhook_Unhook, the program compiles successfully.

Dumpbin suggests that both symbols are present in the static library:

>dumpbin /symbols mhook-test.lib|find "Mhook"
015 00000000 SECT4  notype ()    External     | ?Mhook_SetHook@@YAHPAPAXPAX@Z (i
nt __cdecl Mhook_SetHook(void * *,void *))
122 00000000 SECT3B notype ()    External     | ?Mhook_Unhook@@YAHPAPAX@Z (int _
_cdecl Mhook_Unhook(void * *))
>

I am lost and confused, please help.

Answer 1

Answer: I was apparently mixing C++ and C code - the library at hand was in C++ and my program in C.

I had to add extern C around it, as gleaned from this Using C++ library in C code:

#ifdef __cplusplus
extern "C" {
#endif
BOOL Mhook_SetHook(PVOID *ppSystemFunction, PVOID pHookFunction);
BOOL Mhook_Unhook(PVOID *ppHookedFunction);
#ifdef __cplusplus
} // extern "C"
#endif

Once I had done it, my symbol exports started to look much better:

C:\Users\MACABRE\Documents\Visual Studio 2010\Projects\luahooker\Debug>dumpbin /
exports mhook.lib
Microsoft (R) COFF/PE Dumper Version 10.00.30319.01
Copyright (C) Microsoft Corporation.  All rights reserved.


Dump of file mhook.lib

File Type: LIBRARY

     Exports

       ordinal    name

                  _Mhook_SetHook
                  _Mhook_Unhook