don't access stderr directly

xpra/client/client_base.py

@@ -40,7 +40,7 @@
     )
 from xpra.util import (
     flatten_dict, typedict, updict, parse_simple_dict, noerr, std,
-    repr_ellipsized, ellipsizer, nonl,
+    repr_ellipsized, ellipsizer, nonl, stderr_write,
     envbool, envint, disconnect_is_an_error, dump_all_frames, csv, obsc,
     SERVER_UPGRADE, CONNECTION_ERROR, AUTHENTICATION_FAILED,
     )
@@ -257,8 +257,7 @@ def may_notify(self, nid, summary, body, *args, **kwargs):
 
 
     def handle_deadly_signal(self, signum, _frame=None):
-        sys.stderr.write("\ngot deadly signal %s, exiting\n" % SIGNAMES.get(signum, signum))
-        sys.stderr.flush()
+        stderr_write("\ngot deadly signal %s, exiting\n" % SIGNAMES.get(signum, signum))
         self.cleanup()
         force_quit(128 + signum)
 
@@ -277,8 +276,7 @@ def install_signal_handlers(self):
         def os_signal(signum, _frame=None):
             if self.exit_code is None:
                 try:
-                    sys.stderr.write("\n")
-                    sys.stderr.flush()
+                    stderr_write("\n")
                     log.info("client got signal %s", SIGNAMES.get(signum, signum))
                 except Exception:
                     pass

xpra/client/gobject_client_base.py

@@ -13,7 +13,7 @@
 from xpra.util import (
     u, net_utf8, nonl, sorted_nicely, print_nested_dict, envint, flatten_dict, typedict,
     disconnect_is_an_error, ellipsizer, first_time, csv,
-    repr_ellipsized,
+    repr_ellipsized, stderr_write,
     SERVER_EXIT, DONE,
     )
 from xpra.os_util import (
@@ -36,11 +36,7 @@
 
 
 def errwrite(msg):
-    try:
-        sys.stderr.write(msg)
-        sys.stderr.flush()
-    except (OSError, AttributeError):
-        pass
+    stderr_write(msg)
 
 
 class GObjectXpraClient(GObject.GObject, XpraClientBase):

xpra/gtk_common/gobject_compat.py

@@ -5,10 +5,9 @@
 
 #legacy compatibility file
 
-import sys
 import signal
 
-from xpra.util import dump_all_frames, dump_gc_frames
+from xpra.util import dump_all_frames, dump_gc_frames, stderr_write
 from xpra.os_util import SIGNAMES, POSIX, get_util_logger
 
 
@@ -24,8 +23,7 @@ def write_signal():
         if commandtype is None:
             return
         try:
-            sys.stderr.write("\n")
-            sys.stderr.flush()
+            stderr_write("\n")
             cstr = ""
             if commandtype:
                 cstr = commandtype+" "

xpra/net/ssh.py

@@ -31,7 +31,7 @@
     restore_script_env, get_saved_env,
     WIN32, OSX, POSIX,
     )
-from xpra.util import envint, envbool, envfloat, engs, noerr, csv
+from xpra.util import envint, envbool, envfloat, engs, noerr, csv, stderr_write
 from xpra.log import Logger, is_debug_enabled
 
 #pylint: disable=import-outside-toplevel
@@ -537,7 +537,7 @@ def adddnscheckinfo(q):
                         f"Offending {keyname()} key in {host_keys_filename}",
                         f"ECDSA host key for {keyname()} has changed and you have requested strict checking.",
                         ]
-                    sys.stderr.write(os.linesep.join(qinfo))
+                    stderr_write(os.linesep.join(qinfo))
                     transport.close()
                     raise InitExit(EXIT_SSH_KEY_FAILURE, "SSH Host key has changed")
                 if not confirm(qinfo):

xpra/scripts/config.py

@@ -9,7 +9,7 @@
 import os
 import shlex
 
-from xpra.util import csv, sorted_nicely, remove_dupes
+from xpra.util import csv, sorted_nicely, remove_dupes, stderr_write
 from xpra.os_util import (
     WIN32, OSX, POSIX,
     osexpand, getuid, getgid, get_username_for_uid,
@@ -19,7 +19,7 @@
     )
 
 def warn(msg):
-    sys.stderr.write(msg+"\n")
+    stderr_write(msg+"\n")
 
 def nodebug(*_args):
     #can be overriden

xpra/scripts/main.py

@@ -23,6 +23,7 @@
 from xpra.util import (
     csv, envbool, envint, nonl, pver, engs,
     noerr, sorted_nicely, typedict,
+    stderr_write,
     DEFAULT_PORTS,
     )
 from xpra.exit_codes import (
@@ -81,8 +82,7 @@ def nox():
 
 def werr(*msg):
     for x in msg:
-        noerr(sys.stderr.write, "%s\n" % (x,))
-    noerr(sys.stderr.flush)
+        stderr_write("%s\n" % (x,))
 
 def add_process(*args, **kwargs):
     from xpra.child_reaper import getChildReaper
@@ -96,10 +96,10 @@ def main(script_file, cmdline):
         start_mem_watcher(ml)
 
     if sys.flags.optimize>0:    # pragma: no cover
-        sys.stderr.write("************************************************************\n")
-        sys.stderr.write(f"Warning: the python optimize flag is set to {sys.flags.optimize}\n")
-        sys.stderr.write(" xpra is very likely to crash\n")
-        sys.stderr.write("************************************************************\n")
+        stderr_write("************************************************************\n")
+        stderr_write(f"Warning: the python optimize flag is set to {sys.flags.optimize}\n")
+        stderr_write(" xpra is very likely to crash\n")
+        stderr_write("************************************************************\n")
         time.sleep(5)
 
     from xpra.platform import clean as platform_clean, command_error, command_info
@@ -2239,8 +2239,7 @@ def do_run_glcheck(opts, show=False) -> dict:
         if is_debug_enabled("opengl"):
             log("do_run_glcheck(..)", exc_info=True)
         if use_tty():
-            noerr(sys.stderr.write, "error=%s\n" % nonl(e))
-            noerr(sys.stderr.flush)
+            stderr_write("error=%s\n" % nonl(e))
         return {
             "success"   : False,
             "message"   : str(e).replace("\n", " "),
@@ -2656,7 +2655,7 @@ def run_proxy(error_cb, opts, script_file, cmdline, args, mode, defaults):
             if display_name:
                 state = dotxpra.get_display_state(display_name)
                 if state!=DotXpra.DEAD:
-                    sys.stderr.write(f"found existing display {display_name} : {state}\n")
+                    stderr_write(f"found existing display {display_name} : {state}\n")
         if state!=DotXpra.LIVE:
             #strip defaults, only keep extra ones:
             for x in ("start", "start-child",

xpra/scripts/parsing.py

@@ -8,13 +8,12 @@
 
 #pylint: disable=import-outside-toplevel
 
-import sys
 import shlex
 import os.path
 import optparse
 
 from xpra.version_util import full_version_str
-from xpra.util import envbool, csv, parse_simple_dict, DEFAULT_PORT, DEFAULT_PORTS
+from xpra.util import envbool, csv, parse_simple_dict, DEFAULT_PORT, DEFAULT_PORTS, stderr_write
 from xpra.os_util import WIN32, OSX, POSIX, get_user_uuid
 from xpra.scripts.config import (
     OPTION_TYPES, TRUE_OPTIONS,
@@ -57,30 +56,18 @@ def sound_option(v):
     return bool_or(vl, "disabled", "on", "off", "disabled")
 
 
-def _stderr_write(msg):
-    #use this function to print warnings
-    #we must write to stderr to prevent
-    #the output from interfering when running as proxy over ssh
-    #(which uses stdin / stdout as communication channel)
-    try:
-        sys.stderr.write(msg+"\n")
-        sys.stderr.flush()
-        return True
-    except OSError:
-        return False
-
 def info(msg):
-    if not _stderr_write(msg) and POSIX:
+    if not stderr_write(msg) and POSIX:
         import syslog
         syslog.syslog(syslog.LOG_INFO, msg)
 
 def warn(msg):
-    if not _stderr_write(msg) and POSIX:
+    if not stderr_write(msg) and POSIX:
         import syslog
         syslog.syslog(syslog.LOG_WARNING, msg)
 
 def error(msg):
-    if not _stderr_write(msg) and POSIX:
+    if not stderr_write(msg) and POSIX:
         import syslog
         syslog.syslog(syslog.LOG_ERR, msg)
 

xpra/server/auth/gss_auth.py

@@ -6,7 +6,7 @@
 
 import sys
 
-from xpra.util import typedict
+from xpra.util import typedict, stderr_write
 from xpra.server.auth.sys_auth_base import SysAuthenticatorBase, log, parse_uid, parse_gid
 from xpra.net.digest import get_salt, get_digests, gendigest
 
@@ -63,8 +63,8 @@ def main(argv):
     from xpra.platform import program_context
     with program_context("GSS-Auth", "GSS-Authentication"):
         if len(argv)!=3:
-            sys.stderr.write("%s invalid arguments\n" % argv[0])
-            sys.stderr.write("usage: %s username token\n" % argv[0])
+            stderr_write("%s invalid arguments\n" % argv[0])
+            stderr_write("usage: %s username token\n" % argv[0])
             return 1
         username = argv[1]
         token = argv[2]

xpra/server/auth/kerberos_password_auth.py

@@ -8,7 +8,7 @@
 
 from xpra.server.auth.sys_auth_base import SysAuthenticatorBase, xor, log, parse_uid, parse_gid
 from xpra.net.digest import get_salt, get_digests, gendigest
-from xpra.util import typedict
+from xpra.util import typedict, stderr_write
 from xpra.os_util import WIN32
 
 
@@ -65,8 +65,8 @@ def main(argv):
     from xpra.platform import program_context
     with program_context("Kerberos-Password-Auth", "Kerberos-Password-Authentication"):
         if len(argv) not in (3,4,5):
-            sys.stderr.write("%s invalid arguments\n" % argv[0])
-            sys.stderr.write("usage: %s username password [service [realm]]\n" % argv[0])
+            stderr_write("%s invalid arguments\n" % argv[0])
+            stderr_write("usage: %s username password [service [realm]]\n" % argv[0])
             return 1
         username = argv[1]
         password = argv[2]

xpra/server/auth/kerberos_token_auth.py

@@ -8,7 +8,7 @@
 
 from xpra.server.auth.sys_auth_base import SysAuthenticatorBase, xor, log, parse_uid, parse_gid
 from xpra.net.digest import get_salt, get_digests, gendigest
-from xpra.util import typedict
+from xpra.util import typedict, stderr_write
 from xpra.os_util import WIN32
 
 
@@ -79,8 +79,8 @@ def main(argv):
     from xpra.platform import program_context
     with program_context("Kerberos-Token-Auth", "Kerberos Token Authentication"):
         if len(argv)!=3:
-            sys.stderr.write("%s invalid arguments\n" % argv[0])
-            sys.stderr.write("usage: %s username token\n" % argv[0])
+            stderr_write("%s invalid arguments\n" % argv[0])
+            stderr_write("usage: %s username token\n" % argv[0])
             return 1
         username = argv[1]
         token = argv[2]

xpra/server/auth/ldap3_auth.py

@@ -7,7 +7,7 @@
 import os
 import sys
 
-from xpra.util import obsc, typedict
+from xpra.util import obsc, typedict, stderr_write
 from xpra.server.auth.sys_auth_base import SysAuthenticatorBase, log, parse_uid, parse_gid
 from xpra.log import enable_debug_for, is_debug_enabled
 assert log #tests will disable logging from here
@@ -112,8 +112,8 @@ def main(argv):
                 enable_debug_for("auth")
                 argv.remove(x)
         if len(argv) not in (3,4,5,6):
-            sys.stderr.write("%s invalid arguments\n" % argv[0])
-            sys.stderr.write("usage: %s username password [host] [port] [tls]\n" % argv[0])
+            stderr_write("%s invalid arguments\n" % argv[0])
+            stderr_write("usage: %s username password [host] [port] [tls]\n" % argv[0])
             return 1
         username = argv[1]
         password = argv[2]

xpra/server/auth/ldap_auth.py

@@ -8,7 +8,7 @@
 import sys
 import socket
 
-from xpra.util import envint, obsc, typedict
+from xpra.util import envint, obsc, typedict, stderr_write
 from xpra.os_util import bytestostr
 from xpra.server.auth.sys_auth_base import SysAuthenticatorBase, log, parse_uid, parse_gid
 from xpra.log import is_debug_enabled, enable_debug_for
@@ -133,8 +133,8 @@ def main(argv):
                 enable_debug_for("auth")
                 argv.remove(x)
         if len(argv) not in (3,4,5,6,7):
-            sys.stderr.write("%s invalid arguments\n" % argv[0])
-            sys.stderr.write("usage: %s username password [host] [port] [tls] [username_format]\n" % argv[0])
+            stderr_write("%s invalid arguments\n" % argv[0])
+            stderr_write("usage: %s username password [host] [port] [tls] [username_format]\n" % argv[0])
             return 1
         username = argv[1]
         password = argv[2]

xpra/util.py

@@ -168,6 +168,17 @@ def noerr(fn, *args):
     except Exception:
         return None
 
+def stderr_write(msg:str) -> bool:
+    stderr = sys.stderr
+    if stderr:
+        try:
+            noerr(stderr.write, msg+"\n")
+            noerr(stderr.flush)
+            return True
+        except (OSError, AttributeError):
+            pass
+    return False
+
 
 def net_utf8(value):
     """