From ab4ee6147eb2e8fafd1fb96c945029c789182d3b Mon Sep 17 00:00:00 2001 From: Joel Brobecker Date: Tue, 30 Apr 2019 16:00:19 -0500 Subject: [PATCH] gdb/windows-nat.c: Get rid of main_thread_id global 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) : Do not set main_thread_id. : Replace main_thread_id by current_event.dwThreadId. : Likewise. --- gdb/ChangeLog | 12 ++++++++++++ gdb/windows-nat.c | 11 ++++------- 2 files changed, 16 insertions(+), 7 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 1b4b83d13af..126343ce99b 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,15 @@ +2019-04-30 Joel Brobecker + + * 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) : + Do not set main_thread_id. + : Replace main_thread_id by + current_event.dwThreadId. + : Likewise. + 2019-04-30 Joel Brobecker * windows-nat.c (get_windows_debug_event) : diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c index 9f3242cc405..ae4e3d55b30 100644 --- a/gdb/windows-nat.c +++ b/gdb/windows-nat.c @@ -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: -- 2.30.2