bpo-32030: Rework memory allocators (#4625)

* Fix _PyMem_SetupAllocators("debug"): always restore allocators to
  the defaults, rather than only caling _PyMem_SetupDebugHooks().
* Add _PyMem_SetDefaultAllocator() helper to set the "default"
  allocator.
* Add _PyMem_GetAllocatorsName(): get the name of the allocators
* main() now uses debug hooks on memory allocators if Py_DEBUG is
  defined, rather than calling directly malloc()
* Document default memory allocators in C API documentation
* _Py_InitializeCore() now fails with a fatal user error if
  PYTHONMALLOC value is an unknown memory allocator, instead of
  failing with a fatal internal error.
* Add new tests on the PYTHONMALLOC environment variable
* Add support.with_pymalloc()
* Add the _testcapi.WITH_PYMALLOC constant and expose it as
   support.with_pymalloc().
* sysconfig.get_config_var('WITH_PYMALLOC') doesn't work on Windows, so
   replace it with support.with_pymalloc().
* pythoninfo: add _testcapi collector for pymem

5 files changed, 96 insertions, 23 deletions

diff --git a/Lib/test/pythoninfo.py b/Lib/test/pythoninfo.py
index 85e32a9..7ad076d 100644
--- a/Lib/test/pythoninfo.py
+++ b/Lib/test/pythoninfo.py
@@ -56,6 +56,14 @@ def copy_attributes(info_add, obj, name_fmt, attributes, *, formatter=None):
         info_add(name, value)
 
 
+def copy_attr(info_add, name, mod, attr_name):
+    try:
+        value = getattr(mod, attr_name)
+    except AttributeError:
+        return
+    info_add(name, value)
+
+
 def call_func(info_add, name, mod, func_name, *, formatter=None):
     try:
         func = getattr(mod, func_name)
@@ -168,11 +176,10 @@ def collect_os(info_add):
     call_func(info_add, 'os.gid', os, 'getgid')
     call_func(info_add, 'os.uname', os, 'uname')
 
-    if hasattr(os, 'getgroups'):
-        groups = os.getgroups()
-        groups = map(str, groups)
-        groups = ', '.join(groups)
-        info_add("os.groups", groups)
+    def format_groups(groups):
+        return ', '.join(map(str, groups))
+
+    call_func(info_add, 'os.groups', os, 'getgroups', formatter=format_groups)
 
     if hasattr(os, 'getlogin'):
         try:
@@ -184,11 +191,7 @@ def collect_os(info_add):
         else:
             info_add("os.login", login)
 
-    if hasattr(os, 'cpu_count'):
-        cpu_count = os.cpu_count()
-        if cpu_count:
-            info_add('os.cpu_count', cpu_count)
-
+    call_func(info_add, 'os.cpu_count', os, 'cpu_count')
     call_func(info_add, 'os.loadavg', os, 'getloadavg')
 
     # Get environment variables: filter to list
@@ -219,7 +222,9 @@ def collect_os(info_add):
     )
     for name, value in os.environ.items():
         uname = name.upper()
-        if (uname in ENV_VARS or uname.startswith(("PYTHON", "LC_"))
+        if (uname in ENV_VARS
+           # Copy PYTHON* and LC_* variables
+           or uname.startswith(("PYTHON", "LC_"))
            # Visual Studio: VS140COMNTOOLS
            or (uname.startswith("VS") and uname.endswith("COMNTOOLS"))):
             info_add('os.environ[%s]' % name, value)
@@ -313,12 +318,10 @@ def collect_time(info_add):
     )
     copy_attributes(info_add, time, 'time.%s', attributes)
 
-    if not hasattr(time, 'get_clock_info'):
-        return
-
-    for clock in ('time', 'perf_counter'):
-        tinfo = time.get_clock_info(clock)
-        info_add('time.%s' % clock, tinfo)
+    if hasattr(time, 'get_clock_info'):
+        for clock in ('time', 'perf_counter'):
+            tinfo = time.get_clock_info(clock)
+            info_add('time.%s' % clock, tinfo)
 
 
 def collect_sysconfig(info_add):
@@ -331,7 +334,6 @@ def collect_sysconfig(info_add):
         'CCSHARED',
         'CFLAGS',
         'CFLAGSFORSHARED',
-        'PY_LDFLAGS',
         'CONFIG_ARGS',
         'HOST_GNU_TYPE',
         'MACHDEP',
@@ -339,6 +341,7 @@ def collect_sysconfig(info_add):
         'OPT',
         'PY_CFLAGS',
         'PY_CFLAGS_NODIST',
+        'PY_LDFLAGS',
         'Py_DEBUG',
         'Py_ENABLE_SHARED',
         'SHELL',
@@ -422,6 +425,16 @@ def collect_decimal(info_add):
     copy_attributes(info_add, _decimal, '_decimal.%s', attributes)
 
 
+def collect_testcapi(info_add):
+    try:
+        import _testcapi
+    except ImportError:
+        return
+
+    call_func(info_add, 'pymem.allocator', _testcapi, 'pymem_getallocatorsname')
+    copy_attr(info_add, 'pymem.with_pymalloc', _testcapi, 'WITH_PYMALLOC')
+
+
 def collect_info(info):
     error = False
     info_add = info.add
@@ -444,6 +457,7 @@ def collect_info(info):
         collect_zlib,
         collect_expat,
         collect_decimal,
+        collect_testcapi,
     ):
         try:
             collect_func(info_add)
diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index 42c41ff..f0e1507 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -2848,3 +2848,8 @@ class SaveSignals:
     def restore(self):
         for signum, handler in self.handlers.items():
             self.signal.signal(signum, handler)
+
+
+def with_pymalloc():
+    import _testcapi
+    return _testcapi.WITH_PYMALLOC
diff --git a/Lib/test/test_capi.py b/Lib/test/test_capi.py
index 7a10cda..2a6de3c 100644
--- a/Lib/test/test_capi.py
+++ b/Lib/test/test_capi.py
@@ -654,8 +654,7 @@ class PyMemMallocDebugTests(PyMemDebugTests):
     PYTHONMALLOC = 'malloc_debug'
 
 
-@unittest.skipUnless(sysconfig.get_config_var('WITH_PYMALLOC') == 1,
-                     'need pymalloc')
+@unittest.skipUnless(support.with_pymalloc(), 'need pymalloc')
 class PyMemPymallocDebugTests(PyMemDebugTests):
     PYTHONMALLOC = 'pymalloc_debug'
 
diff --git a/Lib/test/test_cmd_line.py b/Lib/test/test_cmd_line.py
index 7f95fcc..96405e7 100644
--- a/Lib/test/test_cmd_line.py
+++ b/Lib/test/test_cmd_line.py
@@ -5,6 +5,7 @@
 import os
 import subprocess
 import sys
+import sysconfig
 import tempfile
 import unittest
 from test import support
@@ -559,10 +560,14 @@ class CmdLineTest(unittest.TestCase):
         except ImportError:
             pass
         else:
-            code = "import _testcapi; _testcapi.pymem_api_misuse()"
+            code = "import _testcapi; print(_testcapi.pymem_getallocatorsname())"
             with support.SuppressCrashReport():
                 out = self.run_xdev("-c", code, check_exitcode=False)
-            self.assertIn("Debug memory block at address p=", out)
+            if support.with_pymalloc():
+                alloc_name = "pymalloc_debug"
+            else:
+                alloc_name = "malloc_debug"
+            self.assertEqual(out, alloc_name)
 
         try:
             import faulthandler
@@ -573,6 +578,49 @@ class CmdLineTest(unittest.TestCase):
             out = self.run_xdev("-c", code)
             self.assertEqual(out, "True")
 
+    def check_pythonmalloc(self, env_var, name):
+        code = 'import _testcapi; print(_testcapi.pymem_getallocatorsname())'
+        env = dict(os.environ)
+        if env_var is not None:
+            env['PYTHONMALLOC'] = env_var
+        else:
+            env.pop('PYTHONMALLOC', None)
+        args = (sys.executable, '-c', code)
+        proc = subprocess.run(args,
+                              stdout=subprocess.PIPE,
+                              stderr=subprocess.STDOUT,
+                              universal_newlines=True,
+                              env=env)
+        self.assertEqual(proc.stdout.rstrip(), name)
+        self.assertEqual(proc.returncode, 0)
+
+    def test_pythonmalloc(self):
+        # Test the PYTHONMALLOC environment variable
+        pydebug = hasattr(sys, "gettotalrefcount")
+        pymalloc = support.with_pymalloc()
+        if pymalloc:
+            default_name = 'pymalloc_debug' if pydebug else 'pymalloc'
+            default_name_debug = 'pymalloc_debug'
+        else:
+            default_name = 'malloc_debug' if pydebug else 'malloc'
+            default_name_debug = 'malloc_debug'
+
+        tests = [
+            (None, default_name),
+            ('debug', default_name_debug),
+            ('malloc', 'malloc'),
+            ('malloc_debug', 'malloc_debug'),
+        ]
+        if pymalloc:
+            tests.extend((
+                ('pymalloc', 'pymalloc'),
+                ('pymalloc_debug', 'pymalloc_debug'),
+            ))
+
+        for env_var, name in tests:
+            with self.subTest(env_var=env_var, name=name):
+                self.check_pythonmalloc(env_var, name)
+
 
 class IgnoreEnvironmentTest(unittest.TestCase):
 
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 20965b9..4b8fcb9 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -753,8 +753,15 @@ class SysModuleTest(unittest.TestCase):
     @unittest.skipUnless(hasattr(sys, "getallocatedblocks"),
                          "sys.getallocatedblocks unavailable on this build")
     def test_getallocatedblocks(self):
+        try:
+            import _testcapi
+        except ImportError:
+            with_pymalloc = support.with_pymalloc()
+        else:
+            alloc_name = _testcapi.pymem_getallocatorsname()
+            with_pymalloc = (alloc_name in ('pymalloc', 'pymalloc_debug'))
+
         # Some sanity checks
-        with_pymalloc = sysconfig.get_config_var('WITH_PYMALLOC')
         a = sys.getallocatedblocks()
         self.assertIs(type(a), int)
         if with_pymalloc: