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

[Eli Zaretskii <eliz at gnu dot org>]

> Date: Wed, 29 Aug 2012 21:54:37 +0400
> From: LRN <lrn1986@gmail.com>
> 
> 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

What is AeDebug? do you mean the Registry entry of that name?  And
what value should be used in --event= option?

This needs a documentation patch to explain how this option should be
used.

> +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);
> +}

I wonder whether it would be cleaner to have the entire function to be
conditionally compiled on MinGW only.

> @@ -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\

And also this part.

Thanks.