_InterlockedExchange, _InterlockedExchangeAdd have wrong signature

[Braden McDaniel <braden@…>]

Microsoft describes the signature of _InterlockedExchange as

extern "C" LONG  __cdecl _InterlockedExchange(LPLONG volatile Target, LONG Value);

See ​http://msdn2.microsoft.com/en-us/library/f24ya7ct(VS.71).aspx

In boost/detail/intrinsic.hpp, this function gets declared as

extern "C" __declspec(dllimport) long __stdcall InterlockedExchange( long volatile *, long );

The problem is that LPLONG volatile is equivalent to long * volatile, not long volatile *. This results in compilation failures in the presence of a correct declaration of this function; i.e., the compiler complains that you cannot overload C functions.

[Braden McDaniel <braden@…>]

Patch

[Braden McDaniel <braden@…>]

As suggested in the summary, the declaration of _InterlockedExchangeAdd has the same problem.

[Peter Dimov]

On which compiler are you seeing this behavior? The actual declaration in <windows.h> is as follows:

WINBASEAPI LONG WINAPI InterlockedExchange(

IN OUT LONG volatile *Target, IN LONG Value );

with the volatile correctly applied to *Target.

[braden@…]

The compiler is Visual C++ 7.1. The problem arises because code in another dependency has declared the function the way the Microsoft documentation recommends. Since the signatures are different, the compiler complains that an extern "C" function has been overloaded.

[Peter Dimov]

The Microsoft documentation is wrong in this case. If we change the code to be wrong as well, the signatures will no longer match the ones in <windows.h>. The documentation for InterlockedExchange

​http://msdn2.microsoft.com/en-us/library/ms683590.aspx

correctly specifies the signature as taking LONG volatile*. BTW, you can't declare a function parameter as long * volatile, the volatile is ignored.