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gdb/windows-nat.c: Get rid of main_thread_id global

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This global is meant to point to the "main" thread of execution of
the program we are debugging. It is set when attaching to a process
or when receiving a CREATE_PROCESS_DEBUG_EVENT event. The theory at
the time was that this was also going to be the thread receiving
the EXIT_PROCESS_DEBUG_EVENT event.

Unfortunately, we have discovered since then that this is actually
not guaranteed. What this means in practice is that there is moderate
risk that main_thread_id refers to a thread which no longer exists.

This global is used in 3 situations:
  - OUTPUT_DEBUG_STRING_EVENT
  - LOAD_DLL_DEBUG_EVENT
  - UNLOAD_DLL_DEBUG_EVENT

It's not clear why we would need to use the main_thread_id in those cases
instead of using the thread ID provided by the kernel events itself.
So this patch implements this approach, which then allows us to delete
the main_thread_id global.

gdb/testsuite:

	* windows-nat.c (main_thread_id): Delete.
	(handle_output_debug_string): Replace main_thread_id by
	current_event.dwThreadId.
	(fake_create_process): Likewise.
	(get_windows_debug_event) <CREATE_PROCESS_DEBUG_EVENT>:
	Do not set main_thread_id.
	<LOAD_DLL_DEBUG_EVENT>: Replace main_thread_id by
	current_event.dwThreadId.
	<UNLOAD_DLL_DEBUG_EVENT>: Likewise.
This commit is contained in:
Joel Brobecker 2019-04-30 16:00:19 -05:00
parent 8ed5b76ea2
commit ab4ee6147e
2 changed files with 16 additions and 7 deletions
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12
gdb/ChangeLog
View File

@ -1,3 +1,15 @@
2019-04-30 Joel Brobecker <brobecker@adacore.com>
* windows-nat.c (main_thread_id): Delete.
(handle_output_debug_string): Replace main_thread_id by
current_event.dwThreadId.
(fake_create_process): Likewise.
(get_windows_debug_event) <CREATE_PROCESS_DEBUG_EVENT>:
Do not set main_thread_id.
<LOAD_DLL_DEBUG_EVENT>: Replace main_thread_id by
current_event.dwThreadId.
<UNLOAD_DLL_DEBUG_EVENT>: Likewise.
2019-04-30 Joel Brobecker <brobecker@adacore.com>
* windows-nat.c (get_windows_debug_event) <EXIT_PROCESS_DEBUG_EVENT>:

11
gdb/windows-nat.c
View File

@ -237,7 +237,6 @@ static DEBUG_EVENT current_event; /* The current debug event from
WaitForDebugEvent */
static HANDLE current_process_handle; /* Currently executing process */
static windows_thread_info *current_thread; /* Info on currently selected thread */
static DWORD main_thread_id; /* Thread ID of the main thread */
/* Counts of things. */
static int exception_count = 0;
@ -1030,7 +1029,7 @@ handle_output_debug_string (struct target_waitstatus *ourstatus)
ourstatus->kind = TARGET_WAITKIND_STOPPED;
retval = strtoul (p, &p, 0);
if (!retval)
retval = main_thread_id;
retval = current_event.dwThreadId;
else if ((x = (LPCVOID) (uintptr_t) strtoull (p, NULL, 0))
&& ReadProcessMemory (current_process_handle, x,
&saved_context,
@ -1406,14 +1405,13 @@ fake_create_process (void)
(unsigned) GetLastError ());
/* We can not debug anything in that case. */
}
main_thread_id = current_event.dwThreadId;
current_thread
= windows_add_thread (ptid_t (current_event.dwProcessId, 0,
current_event.dwThreadId),
current_event.u.CreateThread.hThread,
current_event.u.CreateThread.lpThreadLocalBase,
true /* main_thread_p */);
return main_thread_id;
return current_event.dwThreadId;
}
void
@ -1611,7 +1609,6 @@ get_windows_debug_event (struct target_ops *ops,
break;
current_process_handle = current_event.u.CreateProcessInfo.hProcess;
main_thread_id = current_event.dwThreadId;
/* Add the main thread. */
th = windows_add_thread
(ptid_t (current_event.dwProcessId, 0,
@ -1656,7 +1653,7 @@ get_windows_debug_event (struct target_ops *ops,
catch_errors (handle_load_dll);
ourstatus->kind = TARGET_WAITKIND_LOADED;
ourstatus->value.integer = 0;
thread_id = main_thread_id;
thread_id = current_event.dwThreadId;
break;
case UNLOAD_DLL_DEBUG_EVENT:
@ -1669,7 +1666,7 @@ get_windows_debug_event (struct target_ops *ops,
catch_errors (handle_unload_dll);
ourstatus->kind = TARGET_WAITKIND_LOADED;
ourstatus->value.integer = 0;
thread_id = main_thread_id;
thread_id = current_event.dwThreadId;
break;
case EXCEPTION_DEBUG_EVENT: