gh-115119: remove TEST_COVERAGE private macro (_decimal module)

[skirpichev]

This amends 9eb3b14. Use unstead Py_DEBUG.

• Issue: Unvendor libmpdec sources #115119

[skirpichev]

CC @zware, @vstinner

[vstinner]

Please change PR title to explain the change rather than referring to a commit sha1. Please elaborate also on why you made this change and what is its purpose.

[vstinner]

So, I had to reverse engineer your change...

This change no longer defines TEST_COVERAGE macro when building the _decimal extension with a Python debug build (--with-pydebug).

It seems like the TEST_COVERAGE macro was introduced by the commit 97b4121 (issue gh-94847 and PR gh-94848) to fix building the _decimal with --with-pydebug --with-lto (debug mode with LTO).

In the libmpdec-2.5.1 copy embedded in Python 3.15, I can see that the TEST_COVERAGE macro has an effect on inlining:

#if defined(_MSC_VER)
#defineALWAYS_INLINE __forceinline
#elif defined (__IBMC__) || defined(LEGACY_COMPILER)
#defineALWAYS_INLINE#undef inline
#defineinline#else#ifdefTEST_COVERAGE#defineALWAYS_INLINE#else#defineALWAYS_INLINE inline __attribute__ ((always_inline))
#endif#endif

The bundled copy of the libmpdec decimal library has been removed in the main branch. So it's no longer needed to define the TEST_COVERAGE variable.

[vstinner]

LGTM

[zware]

I wonder if we should go so far as to do this in Include/pyport.h, but that's not a decision I will be making.