[PATCH v3 22/29] Share some inferior-related Windows code

Tom Tromey
2020-03-13T19:09:04Z

This adds a couple of functions to nat/windows-nat.c and changes gdb
and gdbserver to use them. One function checks the list of pending
stops for a match (not yet used by gdbserver, but will be in a
subsequent patch); and the other is a wrapper for ContinueDebugEvent
that always uses the last "real" stop event.

gdb/ChangeLog
2020-03-13 Tom Tromey <tromey@adacore.com>

* windows-nat.c (windows_continue): Use matching_pending_stop and
continue_last_debug_event.
* nat/windows-nat.h (matching_pending_stop)
(continue_last_debug_event): Declare.
* nat/windows-nat.c (DEBUG_EVENTS): New define.
(matching_pending_stop, continue_last_debug_event): New
functions.

gdbserver/ChangeLog
2020-03-13 Tom Tromey <tromey@adacore.com>

* win32-low.c (child_continue): Call continue_last_debug_event.
---
gdb/ChangeLog | 10 +++++++++
gdb/nat/windows-nat.c | 46 ++++++++++++++++++++++++++++++++++++++++++
gdb/nat/windows-nat.h | 13 ++++++++++++
gdb/windows-nat.c | 28 +++----------------------
gdbserver/ChangeLog | 4 ++++
gdbserver/win32-low.cc | 7 +------
6 files changed, 77 insertions(+), 31 deletions(-)

diff --git a/gdb/nat/windows-nat.c b/gdb/nat/windows-nat.c
index 6bbf41c7b13..2c2454b6f6f 100644
--- a/gdb/nat/windows-nat.c
+++ b/gdb/nat/windows-nat.c
@@ -37,6 +37,10 @@ DWORD desired_stop_thread_id = -1;
std::vector<pending_stop> pending_stops;
EXCEPTION_RECORD siginfo_er;

+/* Note that 'debug_events' must be locally defined in the relevant
+ functions. */
+#define DEBUG_EVENTS(x) if (debug_events) debug_printf x
+
windows_thread_info::~windows_thread_info ()
{
CloseHandle (h);
@@ -312,4 +316,46 @@ handle_exception (struct target_waitstatus *ourstatus, bool debug_exceptions)
#undef DEBUG_EXCEPTION_SIMPLE
}

+/* See nat/windows-nat.h. */
+
+bool
+matching_pending_stop (bool debug_events)
+{
+ /* If there are pending stops, and we might plausibly hit one of
+ them, we don't want to actually continue the inferior -- we just
+ want to report the stop. In this case, we just pretend to
+ continue. See the comment by the definition of "pending_stops"
+ for details on why this is needed. */
+ for (const auto &item : pending_stops)
+ {
+ if (desired_stop_thread_id == -1
+ || desired_stop_thread_id == item.thread_id)
+ {
+ DEBUG_EVENTS (("windows_continue - pending stop anticipated, "
+ "desired=0x%x, item=0x%x\n",
+ desired_stop_thread_id, item.thread_id));
+ return true;
+ }
+ }
+
+ return false;
+}
+
+/* See nat/windows-nat.h. */
+
+BOOL
+continue_last_debug_event (DWORD continue_status, bool debug_events)
+{
+ DEBUG_EVENTS (("ContinueDebugEvent (cpid=%d, ctid=0x%x, %s);\n",
+ (unsigned) last_wait_event.dwProcessId,
+ (unsigned) last_wait_event.dwThreadId,
+ continue_status == DBG_CONTINUE ?
+ "DBG_CONTINUE" : "DBG_EXCEPTION_NOT_HANDLED"));
+
+ return ContinueDebugEvent (last_wait_event.dwProcessId,
+ last_wait_event.dwThreadId,
+ continue_status);
+}
+
+
}
diff --git a/gdb/nat/windows-nat.h b/gdb/nat/windows-nat.h
index a4e0b39fcab..0e9316577ba 100644
--- a/gdb/nat/windows-nat.h
+++ b/gdb/nat/windows-nat.h
@@ -225,6 +225,19 @@ typedef enum
extern handle_exception_result handle_exception
(struct target_waitstatus *ourstatus, bool debug_exceptions);

+/* Return true if there is a pending stop matching
+ desired_stop_thread_id. If DEBUG_EVENTS is true, logging will be
+ enabled. */
+
+extern bool matching_pending_stop (bool debug_events);
+
+/* A simple wrapper for ContinueDebugEvent that continues the last
+ waited-for event. If DEBUG_EVENTS is true, logging will be
+ enabled. */
+
+extern BOOL continue_last_debug_event (DWORD continue_status,
+ bool debug_events);
+
}

#endif
diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index a9656a8c91b..67655dc46e4 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -1239,28 +1239,8 @@ windows_continue (DWORD continue_status, int id, int killed)

desired_stop_thread_id = id;

- /* If there are pending stops, and we might plausibly hit one of
- them, we don't want to actually continue the inferior -- we just
- want to report the stop. In this case, we just pretend to
- continue. See the comment by the definition of "pending_stops"
- for details on why this is needed. */
- for (const auto &item : pending_stops)
- {
- if (desired_stop_thread_id == -1
- || desired_stop_thread_id == item.thread_id)
- {
- DEBUG_EVENTS (("windows_continue - pending stop anticipated, "
- "desired=0x%x, item=0x%x\n",
- desired_stop_thread_id, item.thread_id));
- return TRUE;
- }
- }
-
- DEBUG_EVENTS (("ContinueDebugEvent (cpid=%d, ctid=0x%x, %s);\n",
- (unsigned) last_wait_event.dwProcessId,
- (unsigned) last_wait_event.dwThreadId,
- continue_status == DBG_CONTINUE ?
- "DBG_CONTINUE" : "DBG_EXCEPTION_NOT_HANDLED"));
+ if (matching_pending_stop (debug_events))
+ return TRUE;

for (windows_thread_info *th : thread_list)
if (id == -1 || id == (int) th->tid)
@@ -1333,9 +1313,7 @@ windows_continue (DWORD continue_status, int id, int killed)
th->suspend ();
}

- res = ContinueDebugEvent (last_wait_event.dwProcessId,
- last_wait_event.dwThreadId,
- continue_status);
+ res = continue_last_debug_event (continue_status, debug_events);

if (!res)
error (_("Failed to resume program execution"
diff --git a/gdbserver/win32-low.cc b/gdbserver/win32-low.cc
index 7018083746b..33f64700153 100644
--- a/gdbserver/win32-low.cc
+++ b/gdbserver/win32-low.cc
@@ -433,12 +433,7 @@ child_continue (DWORD continue_status, int thread_id)
});
faked_breakpoint = 0;

- if (!ContinueDebugEvent (current_event.dwProcessId,
- current_event.dwThreadId,
- continue_status))
- return FALSE;
-
- return TRUE;
+ return continue_last_debug_event (continue_status, debug_threads);
}

/* Fetch register(s) from the current thread context. */
--
2.21.1