Re: error_start patch

[Chris Faylor <cgf at cygnus dot com>]

On Tue, May 23, 2000 at 11:10:29AM +0400, Egor Duda wrote:
>Hi!
>
>Tuesday, 23 May, 2000 Chris Faylor cgf@cygnus.com wrote:
>
>I  don't  remember  for  sure,  but  i  think  it's  to  not mess with
>(statically  or dynamically) allocated buffer of unknown length needed
>for GetEnvironmentVariable(). it's possible to write smth like
>
>char dummy[1];
>int required_buffer_length = GetEnvironmentVariable("CYGWIN",dummy,0);
>char p[required_buffer_length+1];
>GetEnvironmentVariable("CYGWIN",p,sizeof(p));
>// tweak error_start in p* and set variable
>
>if you think it's better, i'll change my patch.

Nah.  It's no big deal.  I was just curious.

cgf

>CF> This is very interesting but I'm wondering why you use GetEnvironmentStrings
>CF> rather than GetEnvironmentVariable below.
>
>>>  Below is a patch to prevent cygwin's JIT debugger (specified via
>>>'error_start')   from   being   spawned   recursively,  in  case  when
>>>debugger throws exception itself. It also allows to notify the debugee
>>>that  we've    done    with   debugging   and  it  can  exit in peace.
>>>debugger can post event named
>>>
>>>"cygwin_error_start_event_<debugee_win32_pid>"
>>>
>>>instead of
>>>
>>>(gdb) set keep_looping=0
>>>(gdb) c
>>>
>>>----------------------------------------------------------------------------
>>>2000-05-22  Egor Duda <deo@logos-m.ru>
>>>
>>>        * exceptions.cc (try_to_debug): prevent recursive spawning of JIT
>>>        debugger.
>>>        * exceptions.cc (try_to_debug): treat  special event from debugger
>>>        as command to continue.
>>>
>>>Index: cygwin/exceptions.cc
>>>===================================================================
>>>RCS file: /home/duda_admin/cvs-mirror/src/winsup/cygwin/exceptions.cc,v
>>>retrieving revision 1.17
>>>diff -c -2 -r1.17 exceptions.cc
>>>*** cygwin/exceptions.cc        2000/05/20 05:52:33     1.17
>>>--- cygwin/exceptions.cc        2000/05/22 16:55:40
>>>***************
>>>*** 301,304 ****
>>>--- 301,306 ----
>>>  static int NO_COPY keep_looping = 0;
>>>  
>>>+ #define TIME_TO_WAIT_FOR_DEBUGGER 10000
>>>+ 
>>>  extern "C" int
>>>  try_to_debug ()
>>>***************
>>>*** 330,333 ****
>>>--- 332,350 ----
>>>    ReleaseMutex (title_mutex);
>>>  
>>>+   /* prevent recursive exception handling */
>>>+   char* rawenv = GetEnvironmentStrings () ;
>>>+   for ( char* p = rawenv; *p != '\0'; p = strchr (p, '\0') + 1 )
>>>+     { 
>>>+       if (strncmp ( p, "CYGWIN=", sizeof("CYGWIN=") - 1) == 0)
>>>+         {
>>>+           system_printf ( "%s", p);
>>>+           char* q = strstr ( p, "error_start" ) ;
>>>+           /* replace 'error_start=...' with '_rror_start=...' */
>>>+           if ( q ) *q = '_' ;
>>>+           SetEnvironmentVariable ( "CYGWIN", p+sizeof("CYGWIN=") ) ;
>>>+           break ;
>>>+         }
>>>+     }
>>>+ 
>>>    dbg = CreateProcess (NULL,
>>>                       debugger_command,
>>>***************
>>>*** 349,355 ****
>>>    else
>>>      {
>>>        keep_looping = 1;
>>>!       while (keep_looping)
>>>!       Sleep (10000);
>>>      }
>>>  
>>>--- 366,385 ----
>>>    else
>>>      {
>>>+       char event_name [ sizeof ( "cygwin_error_start_event" ) + 9 ];
>>>+       DWORD win32_pid = GetCurrentProcessId ();
>>>+       __small_sprintf ( event_name, "cygwin_error_start_event%x", win32_pid );
>>>+       HANDLE sync_with_dbg = CreateEvent ( NULL, TRUE, FALSE, event_name );
>>>        keep_looping = 1;
>>>!       while (keep_looping) 
>>>!         {
>>>!           if (sync_with_dbg == NULL)
>>>!             Sleep (TIME_TO_WAIT_FOR_DEBUGGER);
>>>!           else
>>>!             {
>>>!               if (WaitForSingleObject (sync_with_dbg,
>>>!                                        TIME_TO_WAIT_FOR_DEBUGGER) == WAIT_OBJECT_0)
>>>!                 break;
>>>!             }
>>>!          }
>>>      }