From b4e7f7128e66d83ab40b2f2266e73a9480ae5df5 Mon Sep 17 00:00:00 2001
From: Itamar Oren <itamarost@gmail.com>
Date: Wed, 21 Oct 2026 18:00:08 -0700
Subject: [PATCH] gh-144942: Link `$(MODLIBS)` into the macOS shared library
 and framework (GH-159966)

The rules that link `libpython$(LDVERSION).dylib` and the macOS and iOS frameworks don't pass `$(MODLIBS)`, unlike the `libpython$(LDVERSION).so` rule. When a module is built in, for example via `Modules/Setup.local`, the libraries that module needs are left out:

- **`--enable-framework`:** the build fails with undefined symbols.
- **`--enable-shared`:** the dylib is linked with `-undefined dynamic_lookup`, so the build succeeds and the failure only shows up at runtime.

To reproduce, build on macOS with this `Modules/Setup.local`:

```
*static*
_blake2 blake2module.c
```

On `main`:

- **`--enable-framework`:** linking `Python.framework` fails with 12 undefined `_Py_LibHacl_*` symbols.
- **`--enable-shared`:** `nm -u libpython3.16.dylib` lists the same 12 symbols. After `make install`, `python3 -c "import _blake2; _blake2.blake2b(b'abc')"` aborts with `dyld: missing symbol called`, and so does a C program that embeds Python.

With this change, both builds link with no undefined HACL symbols, and `_blake2` works as a built-in module. In default builds `$(MODLIBS)` is empty, so they are unaffected. `test_hashlib`, `test_hmac`, `test_embed` and `test_sysconfig` pass for shared and framework builds, both with and without the `Setup.local` above (macOS 14, arm64). I haven't tested the iOS framework rule, which gets the same one-line change.

python-build-standalone already carries the dylib part of this as a patch ([astral-sh/python-build-standalone#870](https://github.com/astral-sh/python-build-standalone/issues/870)). This PR doesn't remove `-undefined dynamic_lookup`, as the earlier gh-145186 did.
(cherry picked from commit 03864a26212a80fec120137a6161ff7c859d179c)

Co-authored-by: Itamar Oren <itamarost@gmail.com>
---
 Makefile.pre.in                                             | 6 +++---
 .../Build/2026-10-20-20-00-00.gh-issue-144942.MdLibs.rst    | 3 +++
 2 files changed, 6 insertions(+), 3 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Build/2026-10-20-20-00-00.gh-issue-144942.MdLibs.rst

diff --git a/Makefile.pre.in b/Makefile.pre.in
index 7b3e508d819459a..ca46f1a89849763 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -1034,7 +1034,7 @@ libpython3.so:	libpython$(LDVERSION).so
 	$(BLDSHARED) $(NO_AS_NEEDED) -o $@ -Wl,-h$@ $^
 
 libpython$(LDVERSION).dylib: $(LIBRARY_OBJS)
-	 $(CC) -dynamiclib $(PY_CORE_LDFLAGS) -undefined dynamic_lookup -Wl,-install_name,$(prefix)/lib/libpython$(LDVERSION).dylib -Wl,-compatibility_version,$(VERSION) -Wl,-current_version,$(VERSION) -o $@ $(LIBRARY_OBJS) $(DTRACE_OBJS) $(SHLIBS) $(LIBC) $(LIBM); \
+	 $(CC) -dynamiclib $(PY_CORE_LDFLAGS) -undefined dynamic_lookup -Wl,-install_name,$(prefix)/lib/libpython$(LDVERSION).dylib -Wl,-compatibility_version,$(VERSION) -Wl,-current_version,$(VERSION) -o $@ $(LIBRARY_OBJS) $(DTRACE_OBJS) $(MODLIBS) $(SHLIBS) $(LIBC) $(LIBM); \
 
 
 libpython$(VERSION).sl: $(LIBRARY_OBJS)
@@ -1068,7 +1068,7 @@ $(PYTHONFRAMEWORKDIR)/Versions/$(VERSION)/$(PYTHONFRAMEWORK): \
 		-install_name $(PYTHONFRAMEWORKINSTALLNAMEPREFIX)/$(PYTHONFRAMEWORK) \
 		-compatibility_version $(VERSION) \
 		-current_version $(VERSION) \
-		-framework CoreFoundation $(LIBS);
+		-framework CoreFoundation $(MODLIBS) $(LIBS);
 	$(INSTALL) -d -m $(DIRMODE)  \
 		$(PYTHONFRAMEWORKDIR)/Versions/$(VERSION)/Resources/English.lproj
 	$(INSTALL_DATA) $(RESSRCDIR)/Info.plist \
@@ -1089,7 +1089,7 @@ $(PYTHONFRAMEWORKDIR)/$(PYTHONFRAMEWORK): \
 		-install_name $(PYTHONFRAMEWORKINSTALLNAMEPREFIX)/$(PYTHONFRAMEWORK) \
 		-compatibility_version $(VERSION) \
 		-current_version $(VERSION) \
-		-framework CoreFoundation $(LIBS);
+		-framework CoreFoundation $(MODLIBS) $(LIBS);
 	$(INSTALL_DATA) $(RESSRCDIR)/Info.plist $(PYTHONFRAMEWORKDIR)/Info.plist
 
 # This rule builds the Cygwin Python DLL and import library if configured
diff --git a/Misc/NEWS.d/next/Build/2026-10-20-20-00-00.gh-issue-144942.MdLibs.rst b/Misc/NEWS.d/next/Build/2026-10-20-20-00-00.gh-issue-144942.MdLibs.rst
new file mode 100644
index 000000000000000..94b25d67af2fe46
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2026-10-20-20-00-00.gh-issue-144942.MdLibs.rst
@@ -0,0 +1,3 @@
+Fix the macOS shared library and framework builds not linking the libraries
+required by built-in modules, such as the HACL* objects needed by ``_blake2``
+when it is built in via :file:`Modules/Setup.local`.