Re[2]: error_start patch

[Egor Duda <deo at logos-m dot ru>]

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.

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;
>>!             }
>>!          }
>>      }

Egor.            mailto:deo@logos-m.ru ICQ 5165414 FidoNet 2:5020/496.19