[Bug win32/14529] Make gdb capable of JIT-debugging on W32

[LRN <lrn1986@gmail.com>]

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To be a JIT-debugger [1] on Windows, gdb has to be able to signal an
event, which is passed to it by command line. If that is not done, the
process being debugged will not come out of a waiting loop after gdb
attaches to it.
If the event is signaled, Windows will break the loop, and let the
exception fall into gdb's lap (well, stack will be a bit borked, but
that's another issue for another day, and there are ways of working
around it), after gdb user does 'continue'.

The attached patch [2] does exactly that by adding extra
"--event=EVENT" argument, thus AeDebug command line will look like this:
c:\mingw32\bin\gdb.exe --pid=%ld --event=%ld

Here [3] is the changelog entry.
Here [4] is a bug entry on the tracker.

[1] http://msdn.microsoft.com/en-us/library/5hs4b7a6%28v=vs.80%29.aspx
[2] http://sourceware.org/bugzilla/attachment.cgi?id=6619&action=diff
[3] http://sourceware.org/bugzilla/attachment.cgi?id=6620
[4] http://sourceware.org/bugzilla/show_bug.cgi?id=14529

[2] and [3] are also attached.
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From 4554c48a13b22b3ed1b5f5239552e4c959d34cc9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=A0=D1=83=D1=81=D0=BB=D0=B0=D0=BD=20=D0=98=D0=B6=D0=B1=D1?=
 =?UTF-8?q?=83=D0=BB=D0=B0=D1=82=D0=BE=D0=B2?= <lrn1986@gmail.com>
Date: Wed, 29 Aug 2012 17:00:47 +0400
Subject: [PATCH] Make gdb JIT-capable (W32)

Adds the --event=EVENT commandline arugment. After attaching to a process,
gdb will signal that event.
Only does anything on W32. On other platforms the argument is accepted, but
gdb does nothing.
Intended to be used in conjunction with AeDebug on W32.
Can be (and is) used to attach a debugger manually.

PR gdb/14529
---
 gdb/infcmd.c   |   29 +++++++++++++++++++++++++++++
 gdb/inferior.h |    2 ++
 gdb/main.c     |   13 ++++++++++++-
 3 files changed, 43 insertions(+), 1 deletions(-)

diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index 8e2f74e..218f713 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -57,6 +57,11 @@
 #include "continuations.h"
 #include "linespec.h"
 
+#ifdef __MINGW32__
+#include <windows.h>
+#include <inttypes.h>
+#endif
+
 /* Functions exported for general use, in inferior.h: */
 
 void all_registers_info (char *, int);
@@ -2636,6 +2641,30 @@ attach_command (char *args, int from_tty)
   discard_cleanups (back_to);
 }
 
+void
+signal_event_command (char *args, int from_tty)
+{
+  int async_exec = 0;
+  uintmax_t event_id = 0;
+  char *endargs = NULL;
+  struct cleanup *back_to = make_cleanup (null_cleanup, NULL);
+
+  dont_repeat ();		/* Not for the faint of heart */
+
+  event_id = strtoumax (args, &endargs, 10);
+
+  if ((event_id == UINTMAX_MAX && errno == ERANGE) || event_id == 0)
+    error (_("Failed to convert event id `%s' to integer"), args);
+
+#ifdef __MINGW32__
+  SetEvent ((HANDLE) event_id);
+  CloseHandle ((HANDLE) event_id);
+#else
+  /* Does nothing on other platforms */
+#endif
+  discard_cleanups (back_to);
+}
+
 /* We had just found out that the target was already attached to an
    inferior.  PTID points at a thread of this new inferior, that is
    the most likely to be stopped right now, but not necessarily so.
diff --git a/gdb/inferior.h b/gdb/inferior.h
index b2607c3..b9592af 100644
--- a/gdb/inferior.h
+++ b/gdb/inferior.h
@@ -241,6 +241,8 @@ extern void post_create_inferior (struct target_ops *, int);
 
 extern void attach_command (char *, int);
 
+extern void signal_event_command (char *, int);
+
 extern char *get_inferior_args (void);
 
 extern void set_inferior_args (char *);
diff --git a/gdb/main.c b/gdb/main.c
index 326b101..f84c278 100644
--- a/gdb/main.c
+++ b/gdb/main.c
@@ -278,6 +278,7 @@ captured_main (void *data)
   char *symarg = NULL;
   char *execarg = NULL;
   char *pidarg = NULL;
+  char *eventarg = NULL;
   char *corearg = NULL;
   char *pid_or_core_arg = NULL;
   char *cdarg = NULL;
@@ -403,7 +404,8 @@ captured_main (void *data)
       OPT_NOWINDOWS,
       OPT_WINDOWS,
       OPT_IX,
-      OPT_IEX
+      OPT_IEX,
+      OPT_EVENT
     };
     static struct option long_options[] =
     {
@@ -438,6 +440,7 @@ captured_main (void *data)
       {"c", required_argument, 0, 'c'},
       {"pid", required_argument, 0, 'p'},
       {"p", required_argument, 0, 'p'},
+      {"event", required_argument, 0, OPT_EVENT},
       {"command", required_argument, 0, 'x'},
       {"eval-command", required_argument, 0, 'X'},
       {"version", no_argument, &print_version, 1},
@@ -582,6 +585,9 @@ captured_main (void *data)
 	      VEC_safe_push (cmdarg_s, cmdarg_vec, &cmdarg);
 	    }
 	    break;
+	  case OPT_EVENT:
+	    eventarg = optarg;
+	    break;
 	  case 'B':
 	    batch_flag = batch_silent = 1;
 	    gdb_stdout = ui_file_new();
@@ -928,6 +934,10 @@ captured_main (void *data)
 			      !batch_flag, RETURN_MASK_ALL);
     }
 
+  if (eventarg != NULL)
+    catch_command_errors (signal_event_command, eventarg,
+			  !batch_flag, RETURN_MASK_ALL);
+
   if (ttyarg != NULL)
     set_inferior_io_terminal (ttyarg);
 
@@ -1055,6 +1065,7 @@ Options:\n\n\
   --dbx              DBX compatibility mode.\n\
   --directory=DIR    Search for source files in DIR.\n\
   --epoch            Output information used by epoch emacs-GDB interface.\n\
+  --event=EVENT      Signal the EVENT when attached to a process. W32 only.\n\
   --exec=EXECFILE    Use EXECFILE as the executable.\n\
   --fullname         Output information used by emacs-GDB interface.\n\
   --help             Print this message.\n\
-- 
1.7.4


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2012-08-29  Руслан Ижбулатов <lrn1986@gmail.com>

	* infcmd.c, inferior.h, main.c: Add --event=%ld argument for W32 compatibility
	Fix PR gdb/14529.