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Date: 10 Jan 2002 16:43:50 -0500
Message-ID: <20020110214350.30413.qmail@lizard.curl.com>
From: Jonathan Kamens <jik AT curl DOT com>
To: cygwin-developers AT cygwin DOT com
Subject: Am I using dumper.exe correctly?

We're using cygwin-1.3.6-6 on our build servers and current versions
of just about all the other packages.  We get occasional crashes in
cygwin processes during our automated builds, so I decided to debug
them as follows:

1) Build the current CVS repository configured like this:

   CFLAGS="-g -O" configure --enable-threadsafe \
     --enable-extra-threadsafe-checking --enable-debugging \
     --enable-vfork

2) Install the new-cygwin1.dll built above on our build servers as
   cygwin1.dll.

3) Put "error_start=c:\cygwin\bin\dumper.exe" in the CYGWIN
   environment variable.

4) Run builds until we get a coredump.

5) Debug the coredump with gdb -- "gdb -nw foo.exe foo.exe.core".

However, I ran into a few problems (obviously, or I wouldn't be
sending this message :-):

1) Things run Very Slowly with the new version of cygwin1.dll.  If I
   had to guess, I'd guess that --enable-extra-threadsafe-checking is
   probably the culprit.  Can anybody confirm or deny that?

2) To test that things were working as expected, I compiled and ran
   this program:

     main() {
       char *foo = 0;

       foo[0] = '\0';
     }

   It did, indeed, crash and produce the file a.exe.core when I ran
   it.  However, when I tried to run "gdb -nw a.exe a.exe.core", it
   coredumped too.  Note that when I run "gdb -nw a.exe" and type
   "run", it correctly runs the program and shows me that the program
   segfaulted on the assignment line; it apparently only coredumps
   when a core file from dumper is specified on the command line.  It
   also coredumps if I run "gdb -nw a.exe" and then specify "core
   a.exe.core".

My next step will be to recompile gdb with debugging symbols and run
gdb under gdb to try to figure out why it's coredumping.  Before I go
ahead with that, does anybody have any insights into what I might be
doing wrong or any other suggestions?

Thanks,

  jik