[itamaro]

Problem

Programs/_freeze_module and _bootstrap_python are linked with $(LIBRARY_OBJS_OMIT_FROZEN), i.e. with every static module from all Setup files (Setup.local, and all of Setup.stdlib under MODULE_BUILDTYPE=static). As a result a builtin module cannot depend on anything the helpers themselves produce:

• a module whose source includes a header generated by $(FREEZE_MODULE) is a dependency cycle (make: Circular ... dependency dropped, then a compile failure);
• a module referencing a symbol from Modules/getpath.o fails to link _freeze_module, which links Modules/getpath_noop.o instead.

CPython itself already carries a workaround for the second case: the _Py_Get_Getpath_CodeObject() stub in getpath_noop.c, there only because _testinternalcapi gets linked into _freeze_module in MODULE_BUILDTYPE=static builds. That option is not available to out-of-tree Setup.local modules.

The Windows build already does this right: PCbuild/_freeze_module.vcxproj compiles a fixed source list with PC/config_minimal.c.

Change

Link the helpers with the core objects plus the modules of Modules/Setup.bootstrap only. The final libpython/python link is unchanged.

• Modules/makesetup: new -b Setup option marking a Setup file as the bootstrap modules. Their objects and libraries are substituted for _BOOTSTRAP_MODOBJS_ / _BOOTSTRAP_MODLIBS_, and a second table, Modules/config_bootstrap.c, is generated with only those modules. A bootstrap module overridden by an earlier rule (e.g. in Setup.local) keeps the overriding static module for the helpers too.
• Makefile.pre.in: BOOTSTRAP_LIBRARY_OBJS (core + Modules/config_bootstrap.o + $(BOOTSTRAP_MODOBJS)) replaces LIBRARY_OBJS_OMIT_FROZEN in the _freeze_module and _bootstrap_python links. getbuildinfo gets a separate object for the helpers, since its prerequisites include $(MODOBJS).
• configure.ac / configure: pass -b Modules/Setup.bootstrap and move config_bootstrap.c into Modules/.
• Modules/getpath_noop.c: drop the now unnecessary stub.

Testing

Linux x86-64, gcc 13:

• Default build, empty Setup.local: same 37 builtin / 75 shared as before; test_frozen test_embed test_sysconfig test_importlib test_zipimport test_site test_getpath test_capi pass; a second make is a no-op.
• Default build with a Setup.local containing (a) a builtin whose source #includes a header generated by $(FREEZE_MODULE) and (b) a builtin calling _Py_Get_Getpath_CodeObject(): fails on main (circular dependency / missing symbol), builds and works on this branch. nm confirms neither module (nor _asyncio) is in the helpers, while posix is.
• MODULE_BUILDTYPE=static: 105 builtins in python; _testinternalcapi and _ssl are no longer in _freeze_module (37 MB vs 63 MB for python), which exercises the removed stub. Same with a Setup.local override of a bootstrap module (errno): the override reaches the helpers. test_frozen test_embed test_getpath test_sysconfig test_capi test_import test_errno pass.

Notes

• MODULE_DEPS_STATIC=Modules/config.c still recompiles the bootstrap objects whenever Setup.local changes, which relinks the helpers and regenerates all frozen headers — the same cascade as today. A follow-up could emit MODULE_DEPS_BOOTSTRAP=Modules/config_bootstrap.c for -b modules, provided config_bootstrap.c is only rewritten when its content changes.
• Cross builds (iOS, Android, wasm) don't build the helpers and are unaffected; not run here.
• configure was edited in sync with configure.ac; make regen-configure still to be run.