From: pfay AT acl DOT lanl DOT gov (Patrick J. Fay)
Subject: Re: gcc problem: cygwin_except_handler  STATUS_ACCESS_VIOLATION,gdb,trace_back
22 Jan 1998 21:20:40 -0800
Message-ID: <Pine.SGI.3.96.980121003945.14417A-100000.cygnus.gnu-win32@bluemountain.acl.lanl.gov>
References: <199801181950 DOT LAA01684 AT graft DOT XCF DOT Berkeley DOT EDU>
Mime-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
To: Jason Alan Nordwick <nordwick AT graft DOT XCF DOT Berkeley DOT EDU>
Cc: Heinz Schweitzer <heinz_schweitzer AT hp DOT com>, gnu-win32 AT cygnus DOT com

Hello Jason, Heinz etc.
Sorry if you already know this:
try the debugger gdb. It works pretty well. Say I have the
program tst.c:
/pfay/bin 323 > cat tst.c
int mysub(int *myi)
{
    int j;
    printf("Got to %s %d\n",__FILE__,__LINE__);
    j = myi[-1000000];
    return(j);
}
int main()
{
    int i,j,myi[100];
    printf("hello; begin\n");
    mysub(myi);
}
and do:
/pfay/bin 324 > gcc -g tst.c -o tstc
/pfay/bin 326 > gdb -nw tstc.exe
GNU gdb 4.16.1
Copyright 1997 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i386-cygwin32"...
(gdb) run
Starting program: /pfay/bin/tstc.exe
10000000:/WINNT/System32/cygwin.dll
....snip... #skip the dll messages...

Program received signal SIGSEGV, Segmentation fault.
0x401076 in mysub (myi=0x240ed5c) at tst.c:5
5           j = myi[-1000000];
(gdb) bt
#0  0x401076 in mysub (myi=0x240ed5c) at tst.c:5
#1  0x4010bb in main () at tst.c:12
#2  0x100063ba in dll_crt0_1 ()
#3  0x100063cb in dll_crt0 ()
#4  0x401219 in cygwin_crt0 ()
(gdb)

Now this is much better than:
/pfay/bin 327 > ./tstc
hello; begin
Got to tst.c 4
(c:\pfay\bin\tstc.exe 1895) In cygwin_except_handler exc C0000005 at 401076 sp 240EE5C
(c:\pfay\bin\tstc.exe 1895) Exception trapped!
(c:\pfay\bin\tstc.exe 1895) exception C0000005 at 401076
(c:\pfay\bin\tstc.exe 1895) exception: ax 203E56C bx 0 cx F dx FFFFFFFF
(c:\pfay\bin\tstc.exe 1895) exception: si 240F25C di 5 bp 240EE60 sp 240EE5C
(c:\pfay\bin\tstc.exe 1895) exception is: STATUS_ACCESS_VIOLATION
(c:\pfay\bin\tstc.exe 1895) Stack trace:
(c:\pfay\bin\tstc.exe 1895) frame 0: sp = 0x240EC90, pc = 0x10007BB2
(c:\pfay\bin\tstc.exe 1895) frame 1: sp = 0x240ECAC, pc = 0x77F94512
(c:\pfay\bin\tstc.exe 1895) frame 2: sp = 0x240ECD0, pc = 0x77F88EEB
(c:\pfay\bin\tstc.exe 1895) frame 3: sp = 0x240ED5C, pc = 0x77F76266
(c:\pfay\bin\tstc.exe 1895) frame 4: sp = 0x240EE60, pc = 0x4010BB
(c:\pfay\bin\tstc.exe 1895) frame 5: sp = 0x240F004, pc = 0x100063BA
(c:\pfay\bin\tstc.exe 1895) frame 6: sp = 0x240FF94, pc = 0x100063CB
(c:\pfay\bin\tstc.exe 1895) frame 7: sp = 0x240FFA0, pc = 0x401219
(c:\pfay\bin\tstc.exe 1895) frame 8: sp = 0x240FFB0, pc = 0x40103B
(c:\pfay\bin\tstc.exe 1895) frame 9: sp = 0x240FFC0, pc = 0x77F1B304
(c:\pfay\bin\tstc.exe 1895) frame 10: sp = 0x240FFF0, pc = 0x0
(c:\pfay\bin\tstc.exe 1895) End of stack trace

If for some reason you can't run it under the debugger (say
you are doing a post-mortem analysis) then you can use this 
trace_back utility:
/pfay/bin 338 > cat trace_back
#!/bin/sh
gawk -f /pfay/bin/trace_back.awk $*

/pfay/bin 339 > cat trace_back.awk
BEGIN{
  prog_name = ARGV[1];
  abend_file = ARGV[2];
  display_lines = ARGV[3];
  if(display_lines+0==0){display_lines=30;}

  #print ARGC " " ARGV[3];
  #line below is 'if(ARGC&lt;3)' in html
  if(ARGC<3)
  {
    printf("usage: trace_back program_name abend_file_name [count_of_lines_to_display]\n",ARGV[0]);
    exit(0);
  }
  printf("#ARGS=%d prognm=%s,abend_msg_file=%s,display %d lines\n",
   ARGC,prog_name,abend_file, display_lines);
  ARGC=2;
  ARGV[1]=ARGV[2];
  pccnt=0;
}
END{
  #line below is: for(i=1;i&lt;pccnt;i++) (in html)
  for(i=1;i<pccnt;i++)
  {
     str=pcarr[i];
     print  "objdump -d --source --line-numbers --start-address=" str;
         pcpart = substr(str,index(str,"x")+1);
     syscmd="objdump -d --source --line-numbers --start-address=" pcarr[i] " " prog_name " |head -" display_lines;
         system(syscmd);
         close(syscmd);
  }
}
/cygwin_except_handler/{
  i=index($0," at ");
  str=substr($0,i+4);
  arrc=split(str,arr);
  pc="0x" arr[1];
  print "pc=" pc;
  pccnt++;
  pcarr[pccnt]=pc;
}
/ pc = /{
  i=index($0," pc = ");
  str=substr($0,i+5);
  arrc=split(str,arr);
  pc=arr[1];
  print "pc=" pc;
  pccnt++;
  pcarr[pccnt]=pc;
}

/pfay/bin 340 >
To run it, copy the abend message to a file. then do
../trace_back ./tstc.exe abend_file_name [optionally_the_number_of_lines_to_display]
and you get an assembly dump (and if it was compiled with -g, the source code):
(Note that the dll's aren't found by trace_back.)
/pfay/bin 342 > ./tstc.exe >& tmp.jnk   # to put the abend message in tmp.jnk
/pfay/bin 343 > ./trace_back tstc.exe tmp.jnk 30
#ARGS=4 prognm=tstc.exe,abend_msg_file=tmp.jnk,display 30 lines
pc=0x401076
pc=0x10007BB2
pc=0x77F94512
pc=0x77F88EEB
pc=0x77F76266
pc=0x4010BB
pc=0x100063BA
pc=0x100063CB
pc=0x401219
pc=0x40103B
pc=0x77F1B304
pc=0x0
objdump -d --source --line-numbers --start-address=0x401076

tstc.exe:     file format pei-i386

Disassembly of section .text:

00401076 <.LM4+8>:
mysub():
/pfay/bin/tst.c:5
{
    int j;
    printf("Got to %s %d\n",__FILE__,__LINE__);
    j = myi[-1000000];
  401076:       8b 10           movl   (%eax),%edx
  401078:       89 55 fc        movl   %edx,0xfffffffc(%ebp)

0040107b <.LM5>:
/pfay/bin/tst.c:6
    return(j);
  40107b:       8b 55 fc        movl   0xfffffffc(%ebp),%edx
  40107e:       89 d0           movl   %edx,%eax
  401080:       eb 00           jmp    401082 <.LM6>

00401082 <.LM6>:
/pfay/bin/tst.c:7
}
  401082:       c9              leave
  401083:       c3              ret
  401084:       68 65 6c 6c 6f  pushl  $0x6f6c6c65
  401089:       3b 20           cmpl   (%eax),%esp
  40108b:       62 65 67        boundl 0x67(%ebp),%esp
objdump -d --source --line-numbers --start-address=0x10007BB2

tstc.exe:     file format pei-i386

Disassembly of section .text:
objdump -d --source --line-numbers --start-address=0x77F94512

tstc.exe:     file format pei-i386

Disassembly of section .text:
objdump -d --source --line-numbers --start-address=0x77F88EEB

tstc.exe:     file format pei-i386

Disassembly of section .text:
objdump -d --source --line-numbers --start-address=0x77F76266

tstc.exe:     file format pei-i386

Disassembly of section .text:
objdump -d --source --line-numbers --start-address=0x4010BB

tstc.exe:     file format pei-i386

Disassembly of section .text:

004010bb <.LM11+c>:
main():
/pfay/bin/tst.c:12
int main()
{
    int i,j,myi[100];
    printf("hello; begin\n");
    mysub(myi);
  4010bb:       83 c4 04        addl   $0x4,%esp

004010be <.LM12>:
/pfay/bin/tst.c:13
}
  4010be:       c9              leave
  4010bf:       c3              ret

004010c0 <___do_global_dtors>:
__do_global_dtors():
  4010c0:       55              pushl  %ebp
  4010c1:       89 e5           movl   %esp,%ebp
  4010c3:       eb 0e           jmp    4010d3 <___do_global_dtors+13>
  4010c5:       90              nop
  4010c6:       83 c0 04        addl   $0x4,%eax
  4010c9:       a3 04 30 40 00  movl   %eax,0x403004
  4010ce:       8b 40 fc        movl   0xfffffffc(%eax),%eax

/pfay/bin 344 >
If the program wasn't compiled with debug, then you still
get the subroutine names. You can look for 'call <function_name>'
type statements to try and get a context for where the
assembly is in the source code.
More than you ever wanted to know....
Pat






On Sun, 18 Jan 1998, Jason Alan Nordwick wrote:

> 
> Heinz Schweitzer, on Thu 1/15/1998, wrote the following:
> > 
> > (unknown) In cygwin_except_handler
> > (unknown) Exception trapped!
> > (unknown) exception C0000005 at 1001E4B2
> > (unknown) exception: ax 0 bx 0 cx 6 dx 7
> > (unknown) exception: si 6779632D di 36383369 bp 241FB30 sp 241FB30
> > (unknown) exception is: STATUS_ACCESS_VIOLATION
> > (unknown) Stack trace:
> > (unknown) frame 0: sp = 0x241F964, pc = 0x1001282A
> > (unknown) frame 1: sp = 0x241F980, pc = 0x77F94492
> > (unknown) frame 2: sp = 0x241F9A4, pc = 0x77F88E93
> > (unknown) frame 3: sp = 0x241FA30, pc = 0x77F76202
> > (unknown) frame 4: sp = 0x241FB30, pc = 0x10011D4D
> > (unknown) frame 5: sp = 0x241FB44, pc = 0x10018972
> > (unknown) frame 6: sp = 0x241FB5C, pc = 0x10011615
> > (unknown) frame 7: sp = 0x241FF94, pc = 0x10011BFF
> > (unknown) frame 8: sp = 0x241FFA0, pc = 0x4118D5
> > (unknown) frame 9: sp = 0x241FFB0, pc = 0x40103B
> > (unknown) frame 10: sp = 0x241FFC0, pc = 0x77F1B26B
> > (unknown) frame 11: sp = 0x241FFF0, pc = 0x0
> > (unknown) End of stack trace
> > (unknown) In cygwin_except_handler
> > (unknown) Error while dumping state (probably corrupted stack)
> > 
> 
> 
> When I got that error yesterday, it took me two hours to
> figure out that it was the same as SIGBUS.  I was being stoopid
> and derefing a NULL pointer.
> 
> doesn't look like the same problem, but is that always the case ?
> It has nothing to do with a stack corruption, did it ?
> 
> jay
> -- 
> Join the FreeBSD Revolution.
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> 

Patrick Fay, Ph.D., Intel Corp.            email:   pfay AT co DOT intel DOT com
Los Alamos National Lab                    wk:         (505) 665-9141
CTI M.S. B296                              fax:        (505) 667-5921
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