CPython records and propagates several compilation-related flags from the time CPython is built, which in turn are used bydistutils andsetuptools to pass them to extension modules.

Unfortunately afterpypa/distutils#228,distutils now introduced a newLDCXXSHARED, and are using that in preference toLDSHARED when linking C++ code. We do setLDCXXSHARED but we don't propagateLDFLAGS to that variable if the user has set in the environment.

This is a problem because many distributions use the old variableLDFLAGS to propagate linker flags to extension modules (such as hardening and configuration flags) and now these are silently failing for C++ extension modules.

Linked PRs

• gh-123297: Propagate LD_FLAGS to LDCXXSHARED in sysconfig #123298
• [3.13] gh-123297: Propagate LD_FLAGS to LDCXXSHARED in sysconfig (GH-123298) #123319
• [3.12] gh-123297: Propagate LD_FLAGS to LDCXXSHARED in sysconfig (GH-123298) #123320