Re: [PATCH 08/11] [C++/mingw] Simplify first chance exception handling

[Pedro Alves <palves@redhat.com>]

On 11/02/2015 09:01 PM, Simon Marchi wrote:

> Does this change fix something initially related to C++?

Whoops, forgot to mention that in the commit log.  Now updated.

From b2759c57612aa28d19b140a7edf5bac57982564b Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Fri, 30 Oct 2015 20:49:06 +0000
Subject: [PATCH] [C++/mingw] Simplify first chance exception handling

Building in C++ errors out with:

../../src/gdb/windows-nat.c: In function 'int get_windows_debug_event(target_ops*, int, target_waitstatus*)':
../../src/gdb/windows-nat.c:1503:13: warning: invalid conversion from 'int' to 'gdb_signal' [-fpermissive]
    last_sig = 1;
             ^
../../src/gdb/windows-nat.c:1533:43: warning: invalid conversion from 'int' to 'gdb_signal' [-fpermissive]
  windows_resume (ops, minus_one_ptid, 0, 1);
                                           ^
../../src/gdb/windows-nat.c:1228:1: warning:   initializing argument 4 of 'void windows_resume(target_ops*, ptid_t, int, gdb_signal)' [-fpermissive]
 windows_resume (struct target_ops *ops,
 ^

Looking at the code, I can't figure out why we treat first chance
exceptions any different here.

AFAICS, we set last_sig to 1, and then call windows_resume passing
signal==1, so the DBG_EXCEPTION_NOT_HANDLED code path in win32_resume
is taken:

~~~
  if (sig != GDB_SIGNAL_0)
    {
      if (current_event.dwDebugEventCode != EXCEPTION_DEBUG_EVENT)
	{
	  OUTMSG (("Cannot continue with signal %d here.\n", sig));
	}
      else if (sig == last_sig)
	continue_status = DBG_EXCEPTION_NOT_HANDLED;
      else
	OUTMSG (("Can only continue with recieved signal %d.\n", last_sig));
    }
~~~

Fix this by removing this special casing.  gdbserver also goes
straight to continuing with DBG_EXCEPTION_NOT_HANDLED, AFAICS.

gdb/ChangeLog:
2015-11-01  Pedro Alves  <palves@redhat.com>

	* windows-nat.c (handle_exception): Return 0 for first chance
	exceptions.
	(get_windows_debug_event): Adjust.
---
 gdb/windows-nat.c | 24 ++++++------------------
 1 file changed, 6 insertions(+), 18 deletions(-)

diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index cce10f8..a7132d6 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -1124,7 +1124,7 @@ handle_exception (struct target_waitstatus *ourstatus)
     default:
       /* Treat unhandled first chance exceptions specially.  */
       if (current_event.u.Exception.dwFirstChance)
-	return -1;
+	return 0;
       printf_unfiltered ("gdb: unknown target exception 0x%08x at %s\n",
 	(unsigned) current_event.u.Exception.ExceptionRecord.ExceptionCode,
 	host_address_to_string (
@@ -1491,19 +1491,10 @@ get_windows_debug_event (struct target_ops *ops,
 		     "EXCEPTION_DEBUG_EVENT"));
       if (saw_create != 1)
 	break;
-      switch (handle_exception (ourstatus))
-	{
-	case 0:
-	  continue_status = DBG_EXCEPTION_NOT_HANDLED;
-	  break;
-	case 1:
-	  thread_id = current_event.dwThreadId;
-	  break;
-	case -1:
-	  last_sig = 1;
-	  continue_status = -1;
-	  break;
-	}
+      if (handle_exception (ourstatus))
+	thread_id = current_event.dwThreadId;
+      else
+	continue_status = DBG_EXCEPTION_NOT_HANDLED;
       break;
 
     case OUTPUT_DEBUG_STRING_EVENT:	/* Message from the kernel.  */
@@ -1529,10 +1520,7 @@ get_windows_debug_event (struct target_ops *ops,
 
   if (!thread_id || saw_create != 1)
     {
-      if (continue_status == -1)
-	windows_resume (ops, minus_one_ptid, 0, 1);
-      else
-	CHECK (windows_continue (continue_status, -1, 0));
+      CHECK (windows_continue (continue_status, -1, 0));
     }
   else
     {
-- 
1.9.3