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[Cygwin] Fix for: detaching crashes the inferior.
- From: Pedro Alves <pedro_alves at portugalmail dot pt>
- To: gdb-patches at sourceware dot org
- Date: Sun, 08 Apr 2007 12:37:27 +0100
- Subject: [Cygwin] Fix for: detaching crashes the inferior.
Hi all,
Detaching on Cygwin often crashes the inferior, either
when gdb attaches to the inferior, or when gdb launches
the inferior as a child.
Initially I thought that somehow the FLAGS_TRACE_BIT
would be set in the context, and after detaching there would
be no debugger to catch the exception, but it turns out that
it isn't the case - I couldn't find a case where FLAGS_TRACE_BIT
was set. But, surprisingly doing a SetThreadContext with
CONTEXT_CONTROL makes the crashes go away - even if you don't
change the contents of the context. I'm not 100% sure why, but,
it fixes it. If MSFT sends me the Windows sources, I'll look
deeper :)
No regressions on i686-pc-cygwin on XP Pro.
OK?
Cheers,
Pedro Alves
2007-04-08 Pedro Alves <pedro_alves@portugalmail.pt>
* win32-nat.c (win32_detach): Reset the CONTEXT_CONTROL part of
the main thread's context and clear the FLAGS_TRACE_BIT
before detaching.
---
gdb/win32-nat.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
Index: src/gdb/win32-nat.c
===================================================================
--- src.orig/gdb/win32-nat.c 2007-04-08 12:11:22.000000000 +0100
+++ src/gdb/win32-nat.c 2007-04-08 12:11:54.000000000 +0100
@@ -1775,7 +1775,23 @@ win32_detach (char *args, int from_tty)
if (has_detach_ability ())
{
- delete_command (NULL, 0);
+ thread_info *th;
+
+ /* Don't leave breakpoints in the inferior. */
+ remove_breakpoints ();
+
+ /* We also need to reset the thread's context,
+ else we'll get frequent inferior crashes. */
+ th = thread_rec (current_event.dwThreadId, FALSE);
+ th->context.ContextFlags = CONTEXT_CONTROL;
+ win32_fetch_inferior_registers (PS_REGNUM);
+ /* Doing a SetThreadContext with CONTEXT_CONTROL seems to be
+ enough, but let's clear FLAGS_TRACE_BIT just in case
+ somewhere else it gets set. */
+ th->context.EFlags &= ~FLAG_TRACE_BIT;
+ CHECK (SetThreadContext (th->h, &th->context));
+ th->context.ContextFlags = 0;
+
win32_continue (DBG_CONTINUE, -1);
if (!DebugActiveProcessStop (current_event.dwProcessId))
{