Setting breakpoints in a virtual function on a dynamically loaded DLL

Setting breakpoints in a virtual function on a dynamically loaded DLL

[Koon-Seng Lim]

Hi,

I'm trying to set a breakpoint in a virtual function (new_foo::bar())
implemented in a DLL (testdll.dll) which I load dynamically from an .exe
(fooloader.exe). I get the following errors:

$ gdb fooloader.exe
...
(gdb) shared testdll.dll
(gdb)
(gdb) break new_foo::bar
Error: Cannot access memory at address 0x010001014

If I forcibly set a breakpoint at new_foo::bar using the GUI, I get an
error dialog that says "cannot insert breakpoint 1:" and the message
"Error: Cannot access memory at address 0x01000101e" in the console
window.

My question is:
1. Is there any way at all to set a breakpoint in the testdll.dll?
2. Did I doing something silly? The code is very simple and it steps
correctly under the MSVC debugger.

I'm running gdb 5.0 with the Insight GUI on cygwin 1.3.10 on a windows
box. Any help is greatly appreciated!!!

The 3 files listed below are compiled and linked using:

c++ -g -DVERBOSE -DWIN32 -DDLL_EXPORT -I.   -c -o fooloader.o
fooloader.cpp
c++ -g -DVERBOSE -DWIN32 -DDLL_EXPORT -I.   -c -o testdll.o testdll.cpp
c++ -shared -o testdll.dll -mwindows --export-all testdll.o
/lib/libstdc++.a
c++ -o fooloader.exe fooloader.o

--------------------------foo.h -------------------------
class foo {
public:
   virtual void bar() = 0;
};

-----------------------testdll.cpp-----------------------
#include <stdio.h>
#include "foo.h"

#ifdef __cplusplus
extern "C" {
#endif

void *create_object();

#ifdef __cplusplus
}
#endif

class new_foo : foo {
public:
   void bar();
};

void new_foo::bar() {
   printf("in new_foo::bar()\n");
}

void *create_object() {
   return (void *)new new_foo; 
}

-----------------------fooloader.cpp------------------------
#include <windows.h>
#include "foo.h"

typedef void *(*CREATE_OBJECT)();

int main() {
   HMODULE module = LoadLibrary("testdll.dll");
   CREATE_OBJECT create_foo = (CREATE_OBJECT)GetProcAddress(module,
"create_object");
	
   foo *my_foo = (foo *)(create_foo)();
   my_foo->bar();
}

Re: Setting breakpoints in a virtual function on a dynamically loaded DLL

[Daniel Jacobowitz]

On Sun, Mar 31, 2002 at 07:52:31PM -0500, Koon-Seng Lim wrote:
> Hi,
> 
> I'm trying to set a breakpoint in a virtual function (new_foo::bar())
> implemented in a DLL (testdll.dll) which I load dynamically from an .exe
> (fooloader.exe). I get the following errors:
> 
> $ gdb fooloader.exe
> ...
> (gdb) shared testdll.dll
> (gdb)
> (gdb) break new_foo::bar
> Error: Cannot access memory at address 0x010001014
> 
> If I forcibly set a breakpoint at new_foo::bar using the GUI, I get an
> error dialog that says "cannot insert breakpoint 1:" and the message
> "Error: Cannot access memory at address 0x01000101e" in the console
> window.
> 
> My question is:
> 1. Is there any way at all to set a breakpoint in the testdll.dll?
> 2. Did I doing something silly? The code is very simple and it steps
> correctly under the MSVC debugger.
> 
> I'm running gdb 5.0 with the Insight GUI on cygwin 1.3.10 on a windows
> box. Any help is greatly appreciated!!!

- What version of GCC are you using?
- Please try a GDB snapshot; 5.0 is very old now, and has rotten C++
support.

-- 
Daniel Jacobowitz                           Carnegie Mellon University
MontaVista Software                         Debian GNU/Linux Developer

RE: Setting breakpoints in a virtual function on a dynamically loaded DLL

[Koon-Seng Lim]

> -----Original Message-----
> From: Daniel Jacobowitz [mailto:drow@mvista.com]
> Sent: Sunday, March 31, 2002 8:08 PM
> To: Koon-Seng Lim
> Cc: gdb@sources.redhat.com
> Subject: Re: Setting breakpoints in a virtual function on a
dynamically
> loaded DLL
> 
> On Sun, Mar 31, 2002 at 07:52:31PM -0500, Koon-Seng Lim wrote:
> > Hi,
> >
> > I'm trying to set a breakpoint in a virtual function
(new_foo::bar())
> > implemented in a DLL (testdll.dll) which I load dynamically from an
.exe
> > (fooloader.exe). I get the following errors:
> >
> > $ gdb fooloader.exe
> > ...
> > (gdb) shared testdll.dll
> > (gdb)
> > (gdb) break new_foo::bar
> > Error: Cannot access memory at address 0x010001014
> >
> > If I forcibly set a breakpoint at new_foo::bar using the GUI, I get
an
> > error dialog that says "cannot insert breakpoint 1:" and the message
> > "Error: Cannot access memory at address 0x01000101e" in the console
> > window.
> >
> > My question is:
> > 1. Is there any way at all to set a breakpoint in the testdll.dll?
> > 2. Did I doing something silly? The code is very simple and it steps
> > correctly under the MSVC debugger.
> >
> > I'm running gdb 5.0 with the Insight GUI on cygwin 1.3.10 on a
windows
> > box. Any help is greatly appreciated!!!
> 
> - What version of GCC are you using?
> - Please try a GDB snapshot; 5.0 is very old now, and has rotten C++
> support.
> 
> --
> Daniel Jacobowitz                           Carnegie Mellon University
> MontaVista Software                         Debian GNU/Linux Developer

Thanks for the reply!

I'm using gcc version 2.95.3-5. I've just tried out the latest weekly
snapshot(insight+dejagnu-weekly-20020326.tar.bz2) but alas, he problem
remains.

Thanks

-Koon Seng