Strange SAL annotation warning

Question

I'm trying to use Micosoft's SAL annotation for my project, however I get the following warning, and I don't know why.

As an example, I created a new C++ console application, and have this code:

#include <sal.h>

class Whatever
{
public:
    _Check_return_ int Method(__in int number) ;
};

int main()
{
    return 0;
}

When I compile using Visual Studio 2008, I get the following warning:

warning C6540: The use of attribute annotations on this function will invalidate all of its existing __declspec annotations

In the file "c1xxast"

What am I doing wrong? If I remove either the _Check_return_ or the __in, the warning goes away.

I cannot find any reference to the warning C6550. However the same text can be found here: http://msdn.microsoft.com/en-us/library/dd445322.aspx, but it's not very helpful.

Answer 1

The problem may be because you are mixing SAL annotation types. Although made very clear on MSDN, there are two types of SAL annotation: attribute and ... er ... not.

The #defines in <sal.h> VC2005 use the non-attribute versions and start with an underscore followed by a lowercase letter. The newer VC2008 versions expand to compiler attributes and start (and end) with an underscore followed by a capital letter.

You have mixed the two types:

Attribute:

• _In_
• _Check_return_

Non-attribute:

• __in
• __checkReturn

Try changing your annotations to use a single type consistently.

This blog post explains a bit more about this.

Answer 2

You must add SAL annotations to both the declaration and the definition of a method. I'm guessing SAL's upset because it can't find the definition of the method and assumes the attributes are missing.

EDIT Clarification

SAL annotions must appear on both locations for non-abstract methods. For abstract methods SAL will not look for a definition. In certain configurations it will actually ensure that the implementation of the interface has the appropriate notations.