Re: [PATCH V4 00/27] Disabling safe string constraint assertions

["Laszlo Ersek" <lersek@redhat.com>]

On 05/12/20 00:40, Kinney, Michael D wrote:
> Vitaly,
> 
> Thank you for the contribution.
> 
> There are a couple points about this approach that need to be discussed.
> 
> You have included the <Library/DebugCommonLib.h> from 
> MdePkg/Include/Library/DebugLib.h.

Right, I've noticed it. I agree it's unusual. I didn't think it was wrong.

> It is very rare for a 
> lib class to include another lib class.  This means that a module
> that has a dependency on the DebugLib class inherits a hidden
> dependency on the DebugCommonLib class.

I agree.

I think it should be fine. Any header H1 should include such further
headers H2, H3, ... Hn that are required for making the interfaces
declared in H1 usable in client modules.

> For module INF files,
> we require the INF file to list all the lib classes that the
> module sources directly use.

Yes, keyword being "directly".

> Since a module that uses the
> DebugLib uses the ASSERT() and DEBUG() macros, all the APIs
> that the ASSERT() and DEBUG() macros use are also directly
> used by the module.

I believe this is where I disagree. The replacement texts of the
ASSERT() and DEBUG() function-like macros are internals of the
DebugLib.h lib class header, in my opinion. Those internals place
requirements on specific DebugLib instances, not on DebugLib class
consumers.

In other words, when writing a new DebugLib instance, the implementor
has to ensure that the ASSERT() and DEBUG() macros, as defined in the
DebugLib class header, will continue working in DebugLib consumer
modules. The implementor may then choose to make the new DebugLib
instance dependent on the (singleton) DebugCommonLib instance, for
example. (This is being done in patches #3, #4, #16, maybe more.) The
DebugLib consumer module will inherit that dependency, and everything
will work.

Just because ASSERT() and DEBUG() are function-like macros and not
actual functions, I don't think the INF file requirements in
DebugLib-consumer modules should change.

> With this patch series, these macros
> now use the DebugCommonLib class APIs, which means any module
> that uses the DebugLib also directly uses the DebugCommonLib.

In my opinion: indirectly.

Thanks,
Laszlo