Windows: Fix for MSVC6 preprocessor not accepting blank parameters

* unlike later iterations of Visual Studio, MSVC6 does not accept
  blank parameters on macro calls [eg. CALL(a, ,b)]
* blank params were used with the DLL_DECLARE and DLL_LOAD macros
* issue reported by Elmi

diff --git a/libusb/os/windows_usb.h b/libusb/os/windows_usb.h
index b629d18..4fe4916 100644 (file)
--- a/libusb/os/windows_usb.h
+++ b/libusb/os/windows_usb.h
@@ -244,11 +244,11 @@ struct driver_lookup {
 /*
  * API macros - from libusb-win32 1.x
  */
-#define DLL_DECLARE_PREFIXED(api, ret, prefix, name, args)    \
+#define DLL_DECLARE_PREFIXNAME(api, ret, prefixname, name, args)    \
        typedef ret (api * __dll_##name##_t)args;                 \
-       static __dll_##name##_t prefix##name = NULL
+       static __dll_##name##_t prefixname = NULL
 
-#define DLL_LOAD_PREFIXED(dll, prefix, name, ret_on_failure)  \
+#define DLL_LOAD_PREFIXNAME(dll, prefixname, name, ret_on_failure) \
        do {                                                      \
                HMODULE h = GetModuleHandleA(#dll);                   \
        if (!h)                                                   \
@@ -257,18 +257,20 @@ struct driver_lookup {
                if (ret_on_failure) { return LIBUSB_ERROR_NOT_FOUND; }\
                else { break; }                                       \
        }                                                         \
-       prefix##name = (__dll_##name##_t)GetProcAddress(h, #name);\
-       if (prefix##name) break;                                  \
-       prefix##name = (__dll_##name##_t)GetProcAddress(h, #name "A");\
-       if (prefix##name) break;                                  \
-       prefix##name = (__dll_##name##_t)GetProcAddress(h, #name "W");\
-       if (prefix##name) break;                                  \
+       prefixname = (__dll_##name##_t)GetProcAddress(h, #name);       \
+       if (prefixname) break;                                         \
+       prefixname = (__dll_##name##_t)GetProcAddress(h, #name "A");   \
+       if (prefixname) break;                                         \
+       prefixname = (__dll_##name##_t)GetProcAddress(h, #name "W");   \
+       if (prefixname) break;                                         \
        if(ret_on_failure)                                        \
                return LIBUSB_ERROR_NOT_FOUND;                        \
        } while(0)
 
-#define DLL_DECLARE(api, ret, name, args)   DLL_DECLARE_PREFIXED(api, ret, , name, args)
-#define DLL_LOAD(dll, name, ret_on_failure) DLL_LOAD_PREFIXED(dll, , name, ret_on_failure)
+#define DLL_DECLARE(api, ret, name, args)   DLL_DECLARE_PREFIXNAME(api, ret, name, name, args)
+#define DLL_LOAD(dll, name, ret_on_failure) DLL_LOAD_PREFIXNAME(dll, name, name, ret_on_failure)
+#define DLL_DECLARE_PREFIXED(api, ret, prefix, name, args)   DLL_DECLARE_PREFIXNAME(api, ret, prefix##name, name, args)
+#define DLL_LOAD_PREFIXED(dll, prefix, name, ret_on_failure) DLL_LOAD_PREFIXNAME(dll, prefix##name, name, ret_on_failure)
 
 /* OLE32 dependency */
 DLL_DECLARE_PREFIXED(WINAPI, HRESULT, p, CLSIDFromString, (LPCOLESTR, LPCLSID));