Update non-compliance version to allow definition checks

[vmalia]

Problem Statement

When using a definition check,

#ifdef ONEMATH_BLAS_SPEC_VERSION

a preprocessor may evaluate an undefined macro to 0. This means that the existing 000 version for non-compliance is equivalent to the macro not being defined at all and yields the same result for #ifdef.

Solution

To enable the check for definition of the macro itself, meaning, provide different outputs for:

#define ONEMATH_BLAS_SPEC_VERSION 0   // domain non-compliant with specification

case and

// #define ONEMATH_BLAS_SPEC_VERSION   // missing macro definition, may be 0

case, we need to use a number other than 0. 001 is hence proposed as the non-compliance version. It does not conflict with any existing release of the specification. As a natural extension, versions between 001 and 100(Spec release 1.0), can be treated as alpha/beta and used as per special cases that can be defined later as and if needed.

Thanks to @zettai-reido for detecting this issue.

[vmalia]

@rscohn2 @zettai-reido please approve.

[Rbiessy]

I have no issues with this change but I don't understand the motivation for it.

a preprocessor may evaluate an undefined macro to 0

Can you elaborate more on this? This sounds like a compiler issue or a different issue. Which compiler are you using and do you have a reproducer?

This example shows that the ifdef branch should only be taken if a macro is defined on clang: https://gcc.godbolt.org/z/6P6rh5cv5

[zettai-reido]

I have no issues with this change but I don't understand the motivation for it.

a preprocessor may evaluate an undefined macro to 0

Can you elaborate more on this? This sounds like a compiler issue or a different issue. Which compiler are you using and do you have a reproducer?

This example shows that the ifdef branch should only be taken if a macro is defined on clang: https://gcc.godbolt.org/z/6P6rh5cv5

Please try simpler one:

#if X > 0
#warning "X > 0"
#else
#warning "X == 0"
#endif

https://gcc.gnu.org/onlinedocs/cpp/If.html

[Rbiessy]

Thanks for the explanation, that's good to know!
The situation could always be de-ambiguated by checking if defined(X) but maybe it is easier if the version is set to a positive integer.

[vmalia]

@rscohn2 can you please help with the merge?

[Rbiessy]

Is this urgent? I am also able to merge.

[vmalia]

@Rbiessy please go ahead. Not urgent, but trying to close on the spec versioning, since there are oneMKL product changes pending on this PR.