Re: Program-assigned thread names on Windows

LRN
2016-08-10T07:12:06Z

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On 02.08.2016 17:55, Eli Zaretskii wrote:
>> From: LRN
>> Date: Tue, 2 Aug 2016 12:46:47 +0300
>>
>> So, what happens now?
>
> If no one objects in a while, we push.
>

No one seems to object.

I've attached the version of the patch with the named_thread == NULL issue
fixed, and also the ChangeLog and NEWS patches just for the hell of it.

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From 7a4fac770864393b1610b6bccc2e190620e4543e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=A0=D1=83=D1=81=D0=BB=D0=B0=D0=BD=20=D0=98=D0=B6=D0=B1?=
=?UTF-8?q?=D1=83=D0=BB=D0=B0=D1=82=D0=BE=D0=B2?= <lrn1986@gmail.com>
Date: Sun, 26 Jun 2016 11:14:49 +0000
Subject: [PATCH 1/3] Support settings thread name (MS-Windows)

This is done by catching an exception number 0x406D1388
(it has no documented name, though MSDN dubs it "MS_VC_EXCEPTION"
in one code example), which is thrown by the program.
The exception record contains an ID of a thread and a name to
give it.

This requires rolling back some changes in handle_exception(),
which now again returns more than two distinct values. The value
HANDLE_EXCEPTION_IGNORED means that gdb should just continue,
without returning thread ID up the stack (which will result
in further handling of the exception, which is not what we want).
---
gdb/windows-nat.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 69 insertions(+), 8 deletions(-)

diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index 3f67486..8917997 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -174,6 +174,15 @@ static int debug_registers_used;
static int windows_initialization_done;
#define DR6_CLEAR_VALUE 0xffff0ff0

+#define MS_VC_EXCEPTION 0x406D1388
+
+typedef enum
+{
+ HANDLE_EXCEPTION_UNHANDLED = 0,
+ HANDLE_EXCEPTION_HANDLED,
+ HANDLE_EXCEPTION_IGNORED
+} handle_exception_result;
+
/* The string sent by cygwin when it processes a signal.
FIXME: This should be in a cygwin include file. */
#ifndef _CYGWIN_SIGNAL_STRING
@@ -1031,10 +1040,11 @@ display_selectors (char * args, int from_tty)
host_address_to_string (\
current_event.u.Exception.ExceptionRecord.ExceptionAddress))

-static int
+static handle_exception_result
handle_exception (struct target_waitstatus *ourstatus)
{
DWORD code = current_event.u.Exception.ExceptionRecord.ExceptionCode;
+ handle_exception_result result = HANDLE_EXCEPTION_HANDLED;

ourstatus->kind = TARGET_WAITKIND_STOPPED;

@@ -1064,7 +1074,7 @@ handle_exception (struct target_waitstatus *ourstatus)
&& addr < cygwin_load_end))
|| (find_pc_partial_function (addr, &fn, NULL, NULL)
&& startswith (fn, "KERNEL32!IsBad")))
- return 0;
+ return HANDLE_EXCEPTION_UNHANDLED;
}
#endif
break;
@@ -1140,10 +1150,52 @@ handle_exception (struct target_waitstatus *ourstatus)
DEBUG_EXCEPTION_SIMPLE ("EXCEPTION_NONCONTINUABLE_EXCEPTION");
ourstatus->value.sig = GDB_SIGNAL_ILL;
break;
+ case MS_VC_EXCEPTION:
+ if (current_event.u.Exception.ExceptionRecord.NumberParameters >= 3
+ && (current_event.u.Exception.ExceptionRecord.ExceptionInformation[0] & 0xFFFFFFFF) == 0x1000)
+ {
+ long named_thread_id;
+ ptid_t named_thread_ptid;
+ struct thread_info *named_thread;
+ CORE_ADDR thread_name_target;
+ char *thread_name;
+ int thread_name_len;
+
+ DEBUG_EXCEPTION_SIMPLE ("MS_VC_EXCEPTION");
+
+ named_thread_id = (long) (0xFFFFFFFF & current_event.u.Exception.ExceptionRecord.ExceptionInformation[2]);
+ thread_name_target = current_event.u.Exception.ExceptionRecord.ExceptionInformation[1];
+
+ if (named_thread_id == (DWORD) -1)
+ named_thread_id = current_event.dwThreadId;
+
+ named_thread_ptid = ptid_build (current_event.dwProcessId, 0, named_thread_id),
+ named_thread = find_thread_ptid (named_thread_ptid);
+
+ thread_name = NULL;
+ thread_name_len = target_read_string (thread_name_target, &thread_name, 1025, 0);
+ if (thread_name_len > 0 && thread_name != NULL)
+ {
+ thread_name[thread_name_len - 1] = '\0';
+ if (thread_name[0] != '\0' && named_thread != NULL)
+ {
+ xfree (named_thread->name);
+ named_thread->name = thread_name;
+ }
+ else
+ {
+ xfree (thread_name);
+ }
+ }
+ ourstatus->value.sig = GDB_SIGNAL_TRAP;
+ result = HANDLE_EXCEPTION_IGNORED;
+ break;
+ }
+ /* treat improperly formed exception as unknown, fallthrough */
default:
/* Treat unhandled first chance exceptions specially. */
if (current_event.u.Exception.dwFirstChance)
- return 0;
+ return HANDLE_EXCEPTION_UNHANDLED;
printf_unfiltered ("gdb: unknown target exception 0x%08x at %s\n",
(unsigned) current_event.u.Exception.ExceptionRecord.ExceptionCode,
host_address_to_string (
@@ -1153,7 +1205,7 @@ handle_exception (struct target_waitstatus *ourstatus)
}
exception_count++;
last_sig = ourstatus->value.sig;
- return 1;
+ return result;
}

/* Resume thread specified by ID, or all artificially suspended
@@ -1510,10 +1562,19 @@ get_windows_debug_event (struct target_ops *ops,
"EXCEPTION_DEBUG_EVENT"));
if (saw_create != 1)
break;
- if (handle_exception (ourstatus))
- thread_id = current_event.dwThreadId;
- else
- continue_status = DBG_EXCEPTION_NOT_HANDLED;
+ switch (handle_exception (ourstatus))
+ {
+ case HANDLE_EXCEPTION_UNHANDLED:
+ default:
+ continue_status = DBG_EXCEPTION_NOT_HANDLED;
+ break;
+ case HANDLE_EXCEPTION_HANDLED:
+ thread_id = current_event.dwThreadId;
+ break;
+ case HANDLE_EXCEPTION_IGNORED:
+ continue_status = DBG_CONTINUE;
+ break;
+ }
break;

case OUTPUT_DEBUG_STRING_EVENT: /* Message from the kernel. */
--
2.4.0

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From 36200e518eb3645b476ef71d9c897369a9015edb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=A0=D1=83=D1=81=D0=BB=D0=B0=D0=BD=20=D0=98=D0=B6=D0=B1?=
=?UTF-8?q?=D1=83=D0=BB=D0=B0=D1=82=D0=BE=D0=B2?= <lrn1986@gmail.com>
Date: Sat, 23 Jul 2016 08:59:05 +0000
Subject: [PATCH 2/3] Add the thread naming support to NEWS file

---
gdb/NEWS | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/gdb/NEWS b/gdb/NEWS
index b08d8a0..ec813f2 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -77,6 +77,12 @@
The "catch syscall" command now supports catching a group of related
syscalls using the 'group:' or 'g:' prefix.

+* Support for thread names on MS-Windows.
+
+ GDB will catch and correctly handle the special exception that
+ programs running on MS-Windows use to assign names to threads
+ in the debugger.
+
* New commands

skip -file file
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2.4.0

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From f8908dfdc6326ac13ddaed290d3bef336d003b7d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=A0=D1=83=D1=81=D0=BB=D0=B0=D0=BD=20=D0=98=D0=B6=D0=B1?=
=?UTF-8?q?=D1=83=D0=BB=D0=B0=D1=82=D0=BE=D0=B2?= <lrn1986@gmail.com>
Date: Sat, 23 Jul 2016 09:00:38 +0000
Subject: [PATCH 3/3] Add a ChangeLog entry for thread naming on MS-Windows

---
gdb/ChangeLog | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 17c799e..d41d326 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2016-08-10 Руслан Ижбулатов <lrn1986@gmail.com>
+
+ * windows-nat.c (handle_exception): Handle exception 0x406D1388
+ that is used to set thread name.
+ * NEWS: Mention the thread naming support on MS-Windows.
+
2016-08-09 Pedro Alves <palves@redhat.com>

PR gdb/20418
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2.4.0

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