Re: [RFA] Add new cmd line parameter "--pid" for attach.

Michael Snyder
2002-01-10T22:49:54Z

Elena Zannoni wrote:
>
> Michael Snyder writes:
> > Elena Zannoni wrote:
> > >
> > > Michael Snyder writes:
> > > >
> > > > Currently if you invoke gdb as:
> > > >
> > > > gdb filename 12345
> > > >
> > > > gdb will attempt to open a corefile called "12345", and if that
> > > > fails it will print a "file not found" warning, and then attempt
> > > > to attach to a process "12345".
> > > >
> > > > There is a "--core <filename>" command-line argument,
> > > > so that you can specify a corefile without a symbol file:
> > > >
> > > > gdb --core <filename>
> > > >
> > > > but there is no "--pid" option to allow you to specify
> > > > a process-id without a symbol file.
> > > >
> > > > This patch does two things:
> > > >
> > > > 1) Add a "--pid" option to allow specification of an attach pid.
> > > >
> > >
> > > This bit is approved.
> > >
> > > > 2) If the second argument (after the symbol-file) begins with
> > > > a digit, try attach first instead of trying to open it as a
> > > > corefile first. This eliminates the "file not found" warning.
> > > >
> > >
> > > About this, I have a question, what happens if you have a corefile
> > > whose name starts with a digit? I tried it and I get an error:
> > >
> > > [ezannoni@localhost gdb]$ ./gdb -nw ./gdb 2222core
> > > GNU gdb 2002-01-03-cvs
> > > Copyright 2001 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 "i686-pc-linux-gnu"...
> > > Attaching to program: /home/ezannoni/sources/native/gdb/gdb, process 2222
> > > ptrace: No such process.
> > >
> > > then it proceeds normally to figure out it's a core file.
> >
> > Right -- this is actually the reverse of the old behavior
> > (before my change). Previously the algorythm was this:
> >
> > Try to open a corefile
> > on failure, if isdigit(string[0])
> > try to attach a pid.
> >
> > So if it was really a pid, you always got an error when
> > it tried to open it as a corefile. Now the algorythm is:
> >
> > if isdigit (string[0])
> > try to attach a pid
> > on failure, try to open a corefile
> > else try to open a corefile
> >
> > So the only time you will get a failure warning is
> > if you have a corefile whose name begins with a digit.
> > I think that's an improvement (warning should be less
> > frequent).
> >
>
> Yes, that's what I wanted to point out. We are swapping an error
> message with another. The advantage is that the warning shouldn't come
> up as often. Can you commit this, adding the bit to the docs about
> specifying './2222core' instead of '2222core'?

Umm, I can't think of a way to say that, without more-than-doubling
the amount of text currently devoted to the subject. I will check
it in as is, and then we can add something about this if you wish.

> > > I can be convinced that a digit is more likely to indicate a pid than
> > > a corefile, but would there be a way to make that error be silent? I
> > > realize that those error messages are generated in the bowels of gdb,
> > > and it may be really hard to fix that (gee, isn't this something the
> > > insight people have some opinion about? :-)
> > >
>
> Just out of curiosity have you looked into this at all?

No.