bpo-31845: Fix reading flags from environment

Lib/test/test_cmd_line.py

@@ -12,7 +12,6 @@
     spawn_python, kill_python, assert_python_ok, assert_python_failure
 )
 
-
 # XXX (ncoghlan): Move to script_helper and make consistent with run_python
 def _kill_python_and_exit_code(p):
     data = kill_python(p)
@@ -486,6 +485,26 @@ def test_isolatedmode(self):
                                           cwd=tmpdir)
             self.assertEqual(out.strip(), b"ok")
 
+    def test_sys_flags_set(self):
+        # Issue 31845: a startup refactoring broke reading flags from env vars
+        for value, expected in (("", 0), ("1", 1), ("text", 1), ("2", 2)):
+            env_vars = dict(
+                PYTHONDEBUG=value,
+                PYTHONOPTIMIZE=value,
+                PYTHONDONTWRITEBYTECODE=value,
+                PYTHONVERBOSE=value,
+            )
+            code = (
+                "import sys; "
+                "sys.stderr.write(str(sys.flags)); "
+                f"""sys.exit(not (
+                    sys.flags.debug == sys.flags.optimize ==
+                    sys.flags.dont_write_bytecode == sys.flags.verbose ==
+                    {expected}
+                ))"""
+            )
+            with self.subTest(envar_value=value):
+                assert_python_ok('-c', code, **env_vars)
 
 class IgnoreEnvironmentTest(unittest.TestCase):
 
@@ -506,6 +525,20 @@ def test_ignore_PYTHONHASHSEED(self):
         self.run_ignoring_vars("sys.flags.hash_randomization == 1",
                                PYTHONHASHSEED="0")
 
+    def test_sys_flags_not_set(self):
+        # Issue 31845: a startup refactoring broke reading flags from env vars
+        expected_outcome = """
+            (sys.flags.debug == sys.flags.optimize ==
+             sys.flags.dont_write_bytecode == sys.flags.verbose == 0)
+        """
+        self.run_ignoring_vars(
+            expected_outcome,
+            PYTHONDEBUG="1",
+            PYTHONOPTIMIZE="1",
+            PYTHONDONTWRITEBYTECODE="1",
+            PYTHONVERBOSE="1",
+        )
+
 
 def test_main():
     test.support.run_unittest(CmdLineTest, IgnoreEnvironmentTest)

Misc/NEWS.d/next/Core and Builtins/2017-10-24-21-27-32.bpo-31845.8OS-k3.rst

@@ -0,0 +1 @@
+Environment variables are once more read correctly at interpreter startup.

Modules/main.c

@@ -522,39 +522,33 @@ read_command_line(int argc, wchar_t **argv, _Py_CommandLineDetails *cmdline)
     return 0;
 }
 
-static int
-apply_command_line_and_environment(_Py_CommandLineDetails *cmdline)
+static void
+maybe_set_flag(int *flag, int value)
 {
-    char *p;
-    Py_BytesWarningFlag = cmdline->bytes_warning;
-    Py_DebugFlag = cmdline->debug;
-    Py_InspectFlag = cmdline->inspect;
-    Py_InteractiveFlag = cmdline->interactive;
-    Py_IsolatedFlag = cmdline->isolated;
-    Py_OptimizeFlag = cmdline->optimization_level;
-    Py_DontWriteBytecodeFlag = cmdline->dont_write_bytecode;
-    Py_NoUserSiteDirectory = cmdline->no_user_site_directory;
-    Py_NoSiteFlag = cmdline->no_site_import;
-    Py_UnbufferedStdioFlag = cmdline->use_unbuffered_io;
-    Py_VerboseFlag = cmdline->verbosity;
-    Py_QuietFlag = cmdline->quiet_flag;
-
-    if (!Py_InspectFlag &&
-        (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0') {
-        Py_InspectFlag = 1;
-        cmdline->inspect = 1;
-    }
-    if (!cmdline->use_unbuffered_io &&
-        (p = Py_GETENV("PYTHONUNBUFFERED")) && *p != '\0') {
-        Py_UnbufferedStdioFlag = 1;
-        cmdline->use_unbuffered_io = 1;
+    /* Helper to set flag variables from command line options
+    *   - uses the higher of the two values if they're both set
+    *   - otherwise leaves the flag unset
+    */
+    if (*flag < value) {
+        *flag = value;
     }
+}
 
-    if (!Py_NoUserSiteDirectory &&
-        (p = Py_GETENV("PYTHONNOUSERSITE")) && *p != '\0') {
-        Py_NoUserSiteDirectory = 1;
-        cmdline->no_user_site_directory = 1;
-    }
+static int
+apply_command_line_and_environment(_Py_CommandLineDetails *cmdline)
+{
+    maybe_set_flag(&Py_BytesWarningFlag, cmdline->bytes_warning);
+    maybe_set_flag(&Py_DebugFlag, cmdline->debug);
+    maybe_set_flag(&Py_InspectFlag, cmdline->inspect);
+    maybe_set_flag(&Py_InteractiveFlag, cmdline->interactive);
+    maybe_set_flag(&Py_IsolatedFlag, cmdline->isolated);
+    maybe_set_flag(&Py_OptimizeFlag, cmdline->optimization_level);
+    maybe_set_flag(&Py_DontWriteBytecodeFlag, cmdline->dont_write_bytecode);
+    maybe_set_flag(&Py_NoUserSiteDirectory, cmdline->no_user_site_directory);
+    maybe_set_flag(&Py_NoSiteFlag, cmdline->no_site_import);
+    maybe_set_flag(&Py_UnbufferedStdioFlag, cmdline->use_unbuffered_io);
+    maybe_set_flag(&Py_VerboseFlag, cmdline->verbosity);
+    maybe_set_flag(&Py_QuietFlag, cmdline->quiet_flag);
 
     /* TODO: Apply PYTHONWARNINGS & -W options to sys module here */
     /* TODO: Apply -X options to sys module here */

Python/pylifecycle.c

@@ -217,15 +217,18 @@ Py_SetStandardStreamEncoding(const char *encoding, const char *errors)
 
 */
 
-static int
-add_flag(int flag, const char *envs)
+static void
+set_flag(int *flag, const char *envs)
 {
+    /* Helper to set flag variables from environment variables:
+    *   - uses the higher of the two values if they're both set
+    *   - otherwise sets the flag to 1
+    */
     int env = atoi(envs);
-    if (flag < env)
-        flag = env;
-    if (flag < 1)
-        flag = 1;
-    return flag;
+    if (*flag < env)
+        *flag = env;
+    if (*flag < 1)
+        *flag = 1;
 }
 
 static char*
@@ -612,22 +615,28 @@ void _Py_InitializeCore(const _PyCoreConfig *config)
 #endif
 
     if ((p = Py_GETENV("PYTHONDEBUG")) && *p != '\0')
-        Py_DebugFlag = add_flag(Py_DebugFlag, p);
+        set_flag(&Py_DebugFlag, p);
     if ((p = Py_GETENV("PYTHONVERBOSE")) && *p != '\0')
-        Py_VerboseFlag = add_flag(Py_VerboseFlag, p);
+        set_flag(&Py_VerboseFlag, p);
     if ((p = Py_GETENV("PYTHONOPTIMIZE")) && *p != '\0')
-        Py_OptimizeFlag = add_flag(Py_OptimizeFlag, p);
+        set_flag(&Py_OptimizeFlag, p);
+    if ((p = Py_GETENV("PYTHONINSPECT")) && *p != '\0')
+        set_flag(&Py_InspectFlag, p);
     if ((p = Py_GETENV("PYTHONDONTWRITEBYTECODE")) && *p != '\0')
-        Py_DontWriteBytecodeFlag = add_flag(Py_DontWriteBytecodeFlag, p);
+        set_flag(&Py_DontWriteBytecodeFlag, p);
+    if ((p = Py_GETENV("PYTHONNOUSERSITE")) && *p != '\0')
+        set_flag(&Py_NoUserSiteDirectory, p);
+    if ((p = Py_GETENV("PYTHONUNBUFFERED")) && *p != '\0')
+        set_flag(&Py_UnbufferedStdioFlag, p);
     /* The variable is only tested for existence here;
        _Py_HashRandomization_Init will check its value further. */
     if ((p = Py_GETENV("PYTHONHASHSEED")) && *p != '\0')
-        Py_HashRandomizationFlag = add_flag(Py_HashRandomizationFlag, p);
+        set_flag(&Py_HashRandomizationFlag, p);
 #ifdef MS_WINDOWS
     if ((p = Py_GETENV("PYTHONLEGACYWINDOWSFSENCODING")) && *p != '\0')
-        Py_LegacyWindowsFSEncodingFlag = add_flag(Py_LegacyWindowsFSEncodingFlag, p);
+        set_flag(&Py_LegacyWindowsFSEncodingFlag, p);
     if ((p = Py_GETENV("PYTHONLEGACYWINDOWSSTDIO")) && *p != '\0')
-        Py_LegacyWindowsStdioFlag = add_flag(Py_LegacyWindowsStdioFlag, p);
+        set_flag(&Py_LegacyWindowsStdioFlag, p);
 #endif
 
     _Py_HashRandomization_Init(&core_config);