Program-assigned thread names on Windows

LRN
2016-07-23T09:25:41Z

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The attached patch adds thread naming support on Windows.

This works as documented[1] on MSDN - by catching a specific
exception that the program throws.

Setting thread name this way is supported by glib[2] and winpthreads[3] at
least, as well as any program developed with MS toolchain (because WinDbg
supported this for a long time).

[1] https://msdn.microsoft.com/en-us/library/xcb2z8hs.aspx
[2]
https://git.gnome.org/browse/glib/commit/glib/gthread-win32.c?id=e118856430a798bbc529691ad235fd0b0684439d
[3]
https://sourceforge.net/p/mingw-w64/mingw-w64/ci/0d95c795b44b76e1b60dfc119fd93cfd0cb35816/

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From b939b87f06b03653eaea8738752cce1155e908f1 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), 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 code
2 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 | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 50 insertions(+), 5 deletions(-)

diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index 3f67486..01e7954 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -174,6 +174,9 @@ static int debug_registers_used;
static int windows_initialization_done;
#define DR6_CLEAR_VALUE 0xffff0ff0

+#define WINDOWS_THREADNAME_EXCEPTION 0x406D1388
+#define WINDOWS_THREADNAME_EXCEPTION_S "0x406D1388"
+
/* The string sent by cygwin when it processes a signal.
FIXME: This should be in a cygwin include file. */
#ifndef _CYGWIN_SIGNAL_STRING
@@ -1035,6 +1038,7 @@ static int
handle_exception (struct target_waitstatus *ourstatus)
{
DWORD code = current_event.u.Exception.ExceptionRecord.ExceptionCode;
+ int result = 1;

ourstatus->kind = TARGET_WAITKIND_STOPPED;

@@ -1140,6 +1144,38 @@ handle_exception (struct target_waitstatus *ourstatus)
DEBUG_EXCEPTION_SIMPLE ("EXCEPTION_NONCONTINUABLE_EXCEPTION");
ourstatus->value.sig = GDB_SIGNAL_ILL;
break;
+ case WINDOWS_THREADNAME_EXCEPTION:
+ DEBUG_EXCEPTION_SIMPLE (WINDOWS_THREADNAME_EXCEPTION_S);
+ ourstatus->value.sig = GDB_SIGNAL_TRAP;
+ if (current_event.u.Exception.ExceptionRecord.NumberParameters == 4)
+ {
+ DWORD named_thread_id;
+ ptid_t named_thread_ptid;
+ struct thread_info *named_thread;
+ uintptr_t thread_name_target;
+ char *thread_name;
+
+ named_thread_id = (DWORD) current_event.u.Exception.ExceptionRecord.ExceptionInformation[2];
+ thread_name_target = (uintptr_t) 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;
+ if (!target_read_string ((CORE_ADDR) thread_name_target, &thread_name, 1024, 0)
+ || !thread_name || !*thread_name)
+ /* nothing to do */;
+ else
+ {
+ xfree (named_thread->name);
+ named_thread->name = thread_name;
+ }
+ result = 2;
+ }
+ break;
default:
/* Treat unhandled first chance exceptions specially. */
if (current_event.u.Exception.dwFirstChance)
@@ -1153,7 +1189,7 @@ 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 +1546,19 @@ 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 0:
+ default:
+ continue_status = DBG_EXCEPTION_NOT_HANDLED;
+ break;
+ case 1:
+ thread_id = current_event.dwThreadId;
+ break;
+ case 2:
+ continue_status = DBG_CONTINUE;
+ break;
+ }
break;

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

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From d5b4daafe8ee23ef69b47048aa68b9a2542ee740 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 0e339dd..b26df2f 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -60,6 +60,12 @@
for its own control and synchronization, invisible to the command
line.

+* 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 4e7e912d84620950e249c0f10a00e0aad49f7f50 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 0f4a8b6..bd09cb5 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2016-07-23 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.
+
2016-06-30 Руслан Ижбулатов <lrn1986@gmail.com>

PR gdb/14529
--
2.4.0

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