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bug#40271: 26.3; gdb-mode fails to initialize if the target executable i


From: Vladimir Nikishkin
Subject: bug#40271: 26.3; gdb-mode fails to initialize if the target executable is built without symbols
Date: Sat, 28 Mar 2020 21:27:24 +0800

I, personaly, would be happy with just a friendlier error message.

сб, 28 мар. 2020 г. в 21:26, Vladimir Nikishkin <address@hidden>:
>
> Sorry, I misunderstood you.
>
> lockywolf@delllaptop:~$ gdb -i=mi a.out
> =thread-group-added,id="i1"
> ~"GNU gdb (GDB) 9.1\n"
> ~"Copyright (C) 2020 Free Software Foundation, Inc.\n"
> ~"License GPLv3+: GNU GPL version 3 or later
> <http://gnu.org/licenses/gpl.html>\nThis is free software: you are
> free to change and redistribute it.\nThere is NO WARRANTY, to the
> extent permitted by law."
> ~"\nType \"show copying\" and \"show warranty\" for details.\n"
> ~"This GDB was configured as \"x86_64-slackware-linux\".\n"
> ~"Type \"show configuration\" for configuration details.\n"
> ~"For bug reporting instructions, please see:\n"
> ~"<http://www.gnu.org/software/gdb/bugs/>.\n"
> ~"Find the GDB manual and other documentation resources online at:\n
>  <http://www.gnu.org/software/gdb/documentation/>."
> ~"\n\n"
> ~"For help, type \"help\".\n"
> ~"Type \"apropos word\" to search for commands related to \"word\"...\n"
> =cmd-param-changed,param="logging file",value="/home/lockywolf/gdb-log.log"
> =cmd-param-changed,param="print pretty",value="on"
> =cmd-param-changed,param="print array-indexes",value="on"
> =cmd-param-changed,param="print array",value="on"
> =cmd-param-changed,param="print symbol-filename",value="on"
> =cmd-param-changed,param="print object",value="on"
> =cmd-param-changed,param="print vtbl",value="on"
> =cmd-param-changed,param="history save",value="on"
> ~"Reading symbols from a.out...\n"
> (gdb)
> -file-list-exec-source-file
> ^done,line="1",file="../sysdeps/x86_64/start.S",fullname="/root/glibc-2a0c65c5167af50893952729ba38cc68/glibc-2.30/csu/../sysdeps/x86_64/start.S",macro-info="0"
> (gdb)
>
> I am confused, because libc is also expected to be stripped. Is this a gdb 
> bug?
>
> Frankly speaking, I just found this by mistake. I forgot to issue
> -ggdb when compiling my code. I'm not a reverse engineer.
>
> What to do... well, I am not an expert, but the opposite case, that is
> when non-stripped code calls a stripped code function and encounters
> and exception, certainly is handled some way. Maybe gdb-mode can say
> something like "the most recent known file is claimed (by the code) to
> be /root/blah.S, but this file is also missing (just as your debugging
> symbols)". GDB itself does something like this:
> (gdb) list
> 1    ../sysdeps/x86_64/start.S: No such file or directory.
>
> In a perfect world it could ask for an external source address, but
> perhaps this is an overkill
>
>
>
> сб, 28 мар. 2020 г. в 21:12, Eli Zaretskii <address@hidden>:
> >
> > [Please keep the bug address on the CC line, so that this discussion
> > gets recorded by the Emacs issue tracker.]
> >
> > > From: Vladimir Nikishkin <address@hidden>
> > > Date: Sat, 28 Mar 2020 20:38:50 +0800
> > >
> > > I am not super sure how to debug this.
> > >
> > > Firsly, regarding your question:
> > >
> > > lockywolf@delllaptop:~/DevLinux/chibi-sicp$ gdb -i=mi a.out
> > > =thread-group-added,id="i1"
> > > ~"GNU gdb (GDB) 9.1\n"
> > > ~"Copyright (C) 2020 Free Software Foundation, Inc.\n"
> > > ~"License GPLv3+: GNU GPL version 3 or later
> > > <http://gnu.org/licenses/gpl.html>\nThis is free software: you are
> > > free to change and redistribute it.\nThere is NO WARRANTY, to the
> > > extent permitted by law."
> > > ~"\nType \"show copying\" and \"show warranty\" for details.\n"
> > > ~"This GDB was configured as \"x86_64-slackware-linux\".\n"
> > > ~"Type \"show configuration\" for configuration details.\n"
> > > ~"For bug reporting instructions, please see:\n"
> > > ~"<http://www.gnu.org/software/gdb/bugs/>.\n"
> > > ~"Find the GDB manual and other documentation resources online at:\n
> > >  <http://www.gnu.org/software/gdb/documentation/>."
> > > ~"\n\n"
> > > ~"For help, type \"help\".\n"
> > > ~"Type \"apropos word\" to search for commands related to \"word\"...\n"
> > > =cmd-param-changed,param="logging 
> > > file",value="/home/lockywolf/gdb-log.log"
> > > =cmd-param-changed,param="print pretty",value="on"
> > > =cmd-param-changed,param="print array-indexes",value="on"
> > > =cmd-param-changed,param="print array",value="on"
> > > =cmd-param-changed,param="print symbol-filename",value="on"
> > > =cmd-param-changed,param="print object",value="on"
> > > =cmd-param-changed,param="print vtbl",value="on"
> > > =cmd-param-changed,param="history save",value="on"
> > > ~"Reading symbols from a.out...\n"
> > > (gdb)
> > >
> > > Secondly:
> > > The place where gdb-mode fail, IMO, is line 4688 in the gdb-mi.el,
> > > function gdb-get-source-file
> > > I inserted (write-file "/home/lockywolf/debugging-buffer.txt") right
> > > after (goto-char (min-point)), and the contents of the file are:
> > > lockywolf@delllaptop:~$ cat debugging-buffer.1.txt
> > > line="1",file="../sysdeps/x86_64/start.S",fullname="/root/glibc-2a0c65c5167af50893952729ba38cc68/glibc-2.30/csu/../sysdeps/x86_64/start.S",macro-info="0"
> > >
> > > /root/glibc-* is the place where Slackware developers compile glibc.
> > > Doesn't seem like the correct file. The correct file is called
> > > "second.f90", and is in the same directory.
> >
> > That seems to be the problem: in my case I get an error message:
> >
> >   (gdb)
> >   -file-list-exec-source-file
> >   ^error,msg="No symbol table is loaded.  Use the \"file\" command."
> >
> > which is quite expected.
> >
> > So I guess the problem is that your program is stripped, but the
> > standard C library isn't.  What do you suggest Emacs should do in this
> > case?  How can it know that the source file it's been fed isn't the
> > right one?
> >
> > More generally, what is the use case where you want to debug a
> > stripped program in gdb-mi? why did you strip the program in the first
> > place?
>
>
>
> --
> Yours sincerely, Vladimir Nikishkin



-- 
Yours sincerely, Vladimir Nikishkin





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