pythongh-131842: Allow to pass custom CFLAGS and LDFLAGS to the compilation of builtin extension modules

Signed-off-by: Pablo Galindo <[email protected]>

Author: pablogsal

Diff for: Doc/using/configure.rst

@@ -1396,12 +1396,21 @@ Compiler flags
 
    .. versionadded:: 3.2
 
+.. envvar:: PY_EXTRA_STDMODULE_CFLAGS
+
+   Equivalent flag to :envvar:`CFLAGS_NODIST` but it only applies to **all** builtin extension
+   modules built as part of the standard library.
+
+   Default: (empty).
+
+   .. versionadded:: next
+
 .. envvar:: PY_BUILTIN_MODULE_CFLAGS
 
    Compiler flags to build a standard library extension module as a built-in
    module, like the :mod:`posix` module.
 
-   Default: ``$(PY_STDMODULE_CFLAGS) -DPy_BUILD_CORE_BUILTIN``.
+   Default: ``$(BUILTIN_MODULE_CFLAGS) $(PY_STDMODULE_CFLAGS) -DPy_BUILD_CORE_BUILTIN``.
 
    .. versionadded:: 3.8
 
@@ -1495,6 +1504,15 @@ Linker flags
 
    .. versionadded:: 3.8
 
+.. envvar:: PY_EXTRA_STDMODULE_LDFLAGS
+
+   Equivalent flag to :envvar:`LDLAGS_NODIST` but it only applies to **all** builtin extension
+   modules built as part of the standard library.
+
+   Default: (empty).
+
+   .. versionadded:: next
+
 
 .. rubric:: Footnotes
 

Diff for: Doc/whatsnew/3.13.rst

@@ -2591,7 +2591,6 @@ Build Changes
   C extensions are now built with the :ref:`limited C API <limited-c-api>`.
   (Contributed by Victor Stinner in :gh:`85283`.)
 
-
 Porting to Python 3.13
 ======================
 

Diff for: Doc/whatsnew/3.14.rst

@@ -1495,6 +1495,13 @@ Build changes
   with :c:expr:`Py_NO_LINK_LIB`. (Contributed by Jean-Christophe
   Fillion-Robin in :gh:`82909`.)
 
+* Two new configure flags are added: :envvar:`CFLAGS_BUILTIN_MODULE` and
+  :envvar:`LDFLAGS_BUILTIN_MODULE`. These flags allows refistributors to
+  provide compile and linker flags that only apply to standard library extension
+  modules. This is particulary useful to provide options such as ``RUNPATH`` and
+  ``RPATH`` that need to be applied specifically to standard library modules due to
+  its different relative location. (Contributed by Pablo Galindo in :gh:`131842`.)
+
 .. _whatsnew314-pep761:
 
 PEP 761: Discontinuation of PGP signatures

Diff for: Makefile.pre.in

@@ -119,8 +119,11 @@ ARFLAGS=	@ARFLAGS@
 # Extra C flags added for building the interpreter object files.
 CFLAGSFORSHARED=@CFLAGSFORSHARED@
 # C flags used for building the interpreter object files
+PY_EXTRA_STDMODULE_CFLAGS= @PY_EXTRA_STDMODULE_CFLAGS@
+PY_EXTRA_STDMODULE_LDFLAGS= @PY_EXTRA_STDMODULE_LDFLAGS@
 PY_STDMODULE_CFLAGS= $(PY_CFLAGS) $(PY_CFLAGS_NODIST) $(PY_CPPFLAGS) $(CFLAGSFORSHARED)
-PY_BUILTIN_MODULE_CFLAGS= $(PY_STDMODULE_CFLAGS) -DPy_BUILD_CORE_BUILTIN
+PY_BUILTIN_MODULE_CFLAGS= $(PY_EXTRA_STDMODULE_CFLAGS) $(PY_STDMODULE_CFLAGS) -DPy_BUILD_CORE_BUILTIN
+PY_BUILTIN_MODULE_LDFLAGS= $(PY_EXTRA_STDMODULE_LDFLAGS)
 PY_CORE_CFLAGS=	$(PY_STDMODULE_CFLAGS) -DPy_BUILD_CORE
 # Linker flags used for building the interpreter object files
 PY_CORE_LDFLAGS=$(PY_LDFLAGS) $(PY_LDFLAGS_NODIST)

Diff for: Misc/NEWS.d/next/Build/2025-03-28-15-34-49.gh-issue-131842.HB2qep.rst

@@ -0,0 +1,2 @@
+Allow to pass custom ``CFLAGS`` and ``LDFLAGS`` to the compilation of
+builtin extension modules. Patch by Pablo Galindo

Diff for: Modules/makesetup

@@ -274,7 +274,8 @@ sed -e 's/[ 	]*#.*//' -e '/^[ 	]*$/d' |
 				;;
 			esac
 			rule="$file: $objs"
-			rule="$rule; \$(BLDSHARED) $objs $libs \$(LIBPYTHON) -o $file"
+			ldd="\$(BLDSHARED) \$(PY_BUILTIN_MODULE_LDFLAGS)"
+			rule="$rule; $ldd $objs $libs \$(LIBPYTHON) -o $file"
 			echo "$rule" >>$rulesf
 		done
 	done

Diff for: configure

@@ -2432,7 +2432,9 @@ AS_CASE([$enable_wasm_dynamic_linking],
 
 AC_SUBST([BASECFLAGS])
 AC_SUBST([CFLAGS_NODIST])
+AC_SUBST([PY_EXTRA_STDMODULE_CFLAGS])
 AC_SUBST([LDFLAGS_NODIST])
+AC_SUBST([PY_EXTRA_STDMODULE_LDFLAGS])
 AC_SUBST([LDFLAGS_NOLTO])
 AC_SUBST([WASM_ASSETS_DIR])
 AC_SUBST([WASM_STDLIB])