Re: breakpoints and symbol examination problems

["Brian Budge" <brian.budge@gmail.com>]

Lest anyone think this could be a 64 bit issue, this also happens on
my i686 laptop with gdb 6.3.3.

Should I submit a bug to the gdb bug database?  Or could it be this
bug?:  http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27017.  Or is it
another bug, but should be filed in gcc's bug database?

Just for fun, I have tested with many different gcc debug flags
(dwarf-2, gdb, stabs, stabs+ all with various LEVELs), and while gdb
doesn't always report the same error message when I try to examine
locals, it always reports an error message.

Thanks,
  Brian

On Wed, Mar 12, 2008 at 1:14 PM, Brian Budge <brian.budge@gmail.com> wrote:
>
> Hi all -
>
>  This problem reproduces on my other system (opteron), which is running 6.7.1.
>
>  How can I tell if this is lack of debug info from gcc or if this is a
>  gdb problem?
>
>  Thanks,
>   Brian
>
>
>
>   On Tue, Mar 11, 2008 at 2:32 PM, Brian Budge <brian.budge@gmail.com> wrote:
>  > So here is a minimal repro case on my system:
>  >
>  > foo.h
>  > ---------------------------------------------
>  > template<typename joe>
>  > struct Class1 {
>  >    joe a;
>  >
>  >    Class1(int b) : a(b) {}
>  > };
>  >
>  > template<typename joe>
>  > struct Class2 {
>  >    joe a;
>  >
>  >    Class2(const Class1<joe> &rhs) {
>  >        a = 0;
>  >        for(int i = 0; i < 10; ++i) {
>  >            a += rhs.a;
>  >        }
>  >    }
>  > };
>  >
>  > ----------------------------------------------------
>  > foo.cpp
>  > --------------------------------------------------
>  > #include <iostream>
>  > #include "foo.h"
>  >
>  > int main() {
>  >
>  >    Class1<float> c1(15);
>  >
>  >    Class2<float> c2(c1);
>  >
>  >    std::cout << "value is " << c2.a << std::endl;
>  >
>  >    return 0;
>  > }
>  > --------------------------------------------------------------
>  >
>  > I'm compiling foo.cpp with
>  > > g++ -g foo.cpp
>  >
>  > Here's my gdb session:
>  >
>  > GNU gdb 6.7.90.20080311-cvs
>  > Copyright Stuff (removed for brevity)
>  > This GDB was configured as "x86_64-unknown-linux-gnu"...
>  > (gdb) b 8
>  > Breakpoint 1 at 0x40093b: file foo.cpp, line 8.
>  > (gdb) run
>  > Starting program: /home/budge/projects/rt_suite/apps/RtBatch/a.out
>  >
>  > Breakpoint 1, main () at foo.cpp:8
>  > 8           Class2<float> c2(c1);
>  > (gdb) s
>  > Class2 (this=0x7fff23e32c20, rhs=@0x7fff23e32c30) at foo.h:13
>  > 13              a = 0;
>  > (gdb) n
>  > 14              for(int i = 0; i < 10; ++i) {
>  > (gdb)
>  > 15                  a += rhs.a;
>  > (gdb) p i
>  > No symbol "i" in current context.
>  >
>  >
>  > g++ reports version "Gentoo 4.1.1-r3".  I'm running on amd64.
>  >
>  > Hopefully that will help a little in figuring out what is happening.
>  >
>  > Thanks,
>  >  Brian
>  >
>  >
>  >
>  >
>  > On Tue, Mar 11, 2008 at 2:20 PM, Brian Budge <brian.budge@gmail.com> wrote:
>  > > Hi Michael, Daniel, all -
>  > >
>  > >  I built gdb from CVS gdb_6_8-branch, and indeed it fixed my breakpoint
>  > >  problem.  Unfortunately, I still can't examine local variables.  I get
>  > >  this interaction, for example:
>  > >
>  > >  207             vector< dopVertex<T> > tmpVerts;
>  > >  (gdb)
>  > >  208             vector< dopEdge > tmpEdges;
>  > >  (gdb) p tmpVerts
>  > >  No symbol "tmpVerts" in current context.
>  > >
>  > >  Needless to say, not being able to examine your local variable makes
>  > >  debugging fairly tricky ;)
>  > >
>  > >  So, one down, one to go... not too shabby.  Any more ideas?
>  > >
>  > >  Thanks,
>  > >   Brian
>  > >
>  > >
>  > >
>  > >  On Tue, Mar 11, 2008 at 8:24 AM, Brian Budge <brian.budge@gmail.com> wrote:
>  > >  > Actually, this is already with -O0... at least I think.  I'm not
>  > >  >  passing any optimization flags.  For debug symbols I'm passing -ggdb.
>  > >  >
>  > >  >  I'll try the CVS current top of tree a bit later today.
>  > >  >
>  > >  >  Thanks,
>  > >  >   Brian
>  > >  >
>  > >  >
>  > >  >
>  > >  >  On Mon, Mar 10, 2008 at 5:52 PM, Michael Snyder <msnyder@specifix.com> wrote:
>  > >  >  > On Mon, 2008-03-10 at 20:32 -0400, Daniel Jacobowitz wrote:
>  > >  >  >  > On Mon, Mar 10, 2008 at 05:05:17PM -0700, Brian Budge wrote:
>  > >  >  >  >
>  > >  >  >
>  > >  >  > > > Additionally, I can't seem to examine any "stack" variables once in
>  > >  >  >  > > these template functions.  I can see member variables, global
>  > >  >  >  > > variables, and function parameters.
>  > >  >  >  >
>  > >  >  >  > This may be fixed, or it may be a compiler bug.  GCC is not very good
>  > >  >  >  > about emitting local variable information in optimized code.
>  > >  >  >
>  > >  >  >  Can you compile with -O0?
>  > >  >  >
>  > >  >  >
>  > >  >  >
>  > >  >
>  > >
>  >
>