bpo-45847: port _struct to PY_STDLIB_MOD (GH-29706)

Modules/Setup.stdlib.in

@@ -40,6 +40,7 @@
 @MODULE__PICKLE_TRUE@_pickle _pickle.c
 @MODULE__QUEUE_TRUE@_queue _queuemodule.c
 @MODULE__RANDOM_TRUE@_random _randommodule.c
+@MODULE__STRUCT_TRUE@_struct _struct.c
 @MODULE__TYPING_TRUE@_typing _typingmodule.c
 @MODULE__XXSUBINTERPRETERS_TRUE@_xxsubinterpreters _xxsubinterpretersmodule.c
 @MODULE__ZONEINFO_TRUE@_zoneinfo _zoneinfo.c

configure

@@ -718,6 +718,8 @@ MODULE__XXSUBINTERPRETERS_FALSE
 MODULE__XXSUBINTERPRETERS_TRUE
 MODULE__TYPING_FALSE
 MODULE__TYPING_TRUE
+MODULE__STRUCT_FALSE
+MODULE__STRUCT_TRUE
 MODULE_SELECT_FALSE
 MODULE_SELECT_TRUE
 MODULE__RANDOM_FALSE
@@ -20571,6 +20573,15 @@ else
 fi
   as_fn_append MODULE_BLOCK "MODULE_SELECT=yes$as_nl"
 
+     if true; then
+  MODULE__STRUCT_TRUE=
+  MODULE__STRUCT_FALSE='#'
+else
+  MODULE__STRUCT_TRUE='#'
+  MODULE__STRUCT_FALSE=
+fi
+  as_fn_append MODULE_BLOCK "MODULE__STRUCT=yes$as_nl"
+
      if true; then
   MODULE__TYPING_TRUE=
   MODULE__TYPING_FALSE='#'
@@ -22011,6 +22022,10 @@ if test -z "${MODULE_SELECT_TRUE}" && test -z "${MODULE_SELECT_FALSE}"; then
   as_fn_error $? "conditional \"MODULE_SELECT\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
 fi
+if test -z "${MODULE__STRUCT_TRUE}" && test -z "${MODULE__STRUCT_FALSE}"; then
+  as_fn_error $? "conditional \"MODULE__STRUCT\" was never defined.
+Usually this means the macro was only invoked conditionally." "$LINENO" 5
+fi
 if test -z "${MODULE__TYPING_TRUE}" && test -z "${MODULE__TYPING_FALSE}"; then
   as_fn_error $? "conditional \"MODULE__TYPING\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5

configure.ac

@@ -6137,6 +6137,7 @@ PY_STDLIB_MOD_SIMPLE([_posixsubprocess])
 PY_STDLIB_MOD_SIMPLE([_queue])
 PY_STDLIB_MOD_SIMPLE([_random])
 PY_STDLIB_MOD_SIMPLE([select])
+PY_STDLIB_MOD_SIMPLE([_struct])
 PY_STDLIB_MOD_SIMPLE([_typing])
 PY_STDLIB_MOD_SIMPLE([_xxsubinterpreters])
 PY_STDLIB_MOD_SIMPLE([_zoneinfo])

setup.py

@@ -1023,6 +1023,7 @@ def detect_simple_extensions(self):
 
         self.addext(Extension("_queue", ["_queuemodule.c"]))
         self.addext(Extension("_statistics", ["_statisticsmodule.c"]))
+        self.addext(Extension("_struct", ["_struct.c"]))
         self.addext(Extension("_typing", ["_typingmodule.c"]))
 
         # Modules with some UNIX dependencies -- on by default:
@@ -1446,6 +1447,9 @@ def detect_uuid(self):
             self.missing.append('_uuid')
 
     def detect_modules(self):
+        # remove dummy extension
+        self.extensions = []
+
         self.configure_compiler()
         self.init_inc_lib_dirs()
 
@@ -2100,9 +2104,9 @@ class DummyProcess:
                       'build_scripts': PyBuildScripts,
                       'install': PyBuildInstall,
                       'install_lib': PyBuildInstallLib},
-          # The struct module is defined here, because build_ext won't be
+          # A dummy module is defined here, because build_ext won't be
           # called unless there's at least one extension module defined.
-          ext_modules=[Extension('_struct', ['_struct.c'])],
+          ext_modules=[Extension('_dummy', ['_dummy.c'])],
 
           # If you change the scripts installed here, you also need to
           # check the PyBuildScripts command above, and change the links