Re: breakpoints and symbol examination problems

Brian Budge
2008-03-11T21:32:29Z

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?
> > >
> > >
> > >
> >
>