Archer in Cygwin help

Archer in Cygwin help

[Sreejith]

Hi,
          I am trying to use Eclipse-cygwin environment to debug STL.
Currently Eclipse shows the row gdb out put when inspecting STL
container objects. With support from Cygwin mailing list, I could
compile archer in Cygwin to enable python scripting in gdb. I used git
to pull the head revision. By printing a constant using 'python print'
I could confirm that python support is available in Cygwin, but
libstdc++ printers are not working as expected. The following log
explains more:

$ ./gdb.exe ../../a.exe
GNU gdb (GDB) 6.8.50.20090106-cvs
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-pc-cygwin".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
(gdb) l
1       #include <list>
2
3       using namespace std;
4
5       int main ()
6       {
7               list<int> myList;
8
9               for(int i=0; i<10; i++)
10              {
(gdb) l
11                      myList.push_back(i);
12              }
13              return 0;
14      }
(gdb) break 13
Breakpoint 1 at 0x401139: file list.cpp, line 13.
(gdb) run
Starting program: /home/sreejith/archer/a.exe
[New Thread 336.0x8e0]
[New Thread 336.0x1b8]

Breakpoint 1, main () at list.cpp:13
13              return 0;
(gdb) python print 10
10
(gdb) print myList
$1 = {<_List_base<int, std::allocator<int> >> = {
    _M_impl = {<allocator<std::_List_node<int> >> = {<new_allocator<std::_List_n
ode<int> >> = {<No data fields>}, <No data fields>}, _M_node = {
        _M_next = 0x681838, _M_prev = 0x6818c8}}}, <No data fields>}
(gdb) python print myList
Traceback (most recent call last):
  File "<string>", line 1, in <module>
NameError: name 'myList' is not defined
Error while executing Python code.

Any suggestions to fix this issue?

Thanks,
Sreejith

Re: Archer in Cygwin help

[Phil Muldoon]

Sreejith wrote:
> I could confirm that python support is available in Cygwin, but
> libstdc++ printers are not working as expected. The following log
> explains more:
>   

If you building from the archer-tromey-python branch, type:

 python import gdb.libstdcxx.v6.printers

in GDB first. In the Fedora 11 release this is all processed via hooks 
so it is not necessary, but from that branch it is.


> (gdb) python print myList
> Traceback (most recent call last):
>   File "<string>", line 1, in <module>
> NameError: name 'myList' is not defined
> Error while executing Python code.
>   

Python is expecting to find a Python variable "myList" (which doesn't 
exist). If you type the above import statement, and type:

print myList

in GDB, does it work for you then?

Regards

Phil

Re: Archer in Cygwin help

[Sreejith]

2009/5/21 Phil Muldoon <pmuldoon@redhat.com>:
> Sreejith wrote:
>>
>> I could confirm that python support is available in Cygwin, but
>> libstdc++ printers are not working as expected. The following log
>> explains more:
>>
>
> If you building from the archer-tromey-python branch, type:
>
> python import gdb.libstdcxx.v6.printers
>
> in GDB first. In the Fedora 11 release this is all processed via hooks so it
> is not necessary, but from that branch it is.
>
>
>> (gdb) python print myList
>> Traceback (most recent call last):
>>  File "<string>", line 1, in <module>
>> NameError: name 'myList' is not defined
>> Error while executing Python code.
>>
>
> Python is expecting to find a Python variable "myList" (which doesn't
> exist). If you type the above import statement, and type:
>
> print myList
>
> in GDB, does it work for you then?

Thanks for your reply. I tried importing gdb.libstdcxx.v6.printers,
but couldn't succeed. Please see the following log:

$ ./gdb.exe ../../src/a.exe
GNU gdb (GDB) 6.8.50.20090509-cvs
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-pc-cygwin".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...

(gdb) python import gdb.libstdcxx.v6.printers
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: No module named libstdcxx.v6.printers
Error while executing Python code.

You can find the GDB version also. I guess libstdcxx.v6.printers is a
python module and the above error looks like some thing is missing in
gdb initialization? Please give your comments.

Thanks,
Sreejith

Re: Archer in Cygwin help

[Phil Muldoon]

Sreejith wrote:
> 2009/5/21 Phil Muldoon <pmuldoon@redhat.com>:
>   
>> Sreejith wrote:
>>     
> Thanks for your reply. I tried importing gdb.libstdcxx.v6.printers,
> but couldn't succeed. Please see the following log:
>
>
> (gdb) python import gdb.libstdcxx.v6.printers
> Traceback (most recent call last):
>   File "<string>", line 1, in <module>
> ImportError: No module named libstdcxx.v6.printers
> Error while executing Python code

Hi

Are you building this from source? If so which branch are you building? 
Or did you install gdb from somewhere?

Regards

Phil

Re: Archer in Cygwin help

[Sreejith]

2009/5/21 Phil Muldoon <pmuldoon@redhat.com>:
> Sreejith wrote:
>>
>> 2009/5/21 Phil Muldoon <pmuldoon@redhat.com>:
>>
>>>
>>> Sreejith wrote:
>>>
>>
>> Thanks for your reply. I tried importing gdb.libstdcxx.v6.printers,
>> but couldn't succeed. Please see the following log:
>>
>>
>> (gdb) python import gdb.libstdcxx.v6.printers
>> Traceback (most recent call last):
>>  File "<string>", line 1, in <module>
>> ImportError: No module named libstdcxx.v6.printers
>> Error while executing Python code
>
> Hi
>
> Are you building this from source? If so which branch are you building? Or
> did you install gdb from somewhere?
I used a snapshot from git:
http://sourceware.org/git/gitweb.cgi?p=archer.git;a=tree . But today I
cloned archer.git
 and checked out archer-tromey-python branch. Now I am getting a
different error. Please see the log below:

$ ./gdb ../../a.exe
GNU gdb (GDB) 6.8.50.20090106-cvs
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-pc-cygwin".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
(gdb) python import gdb.libstdcxx.v6.printers
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/sreejith/archer/install/share/gdb/python/gdb/libstdcxx/v6/printers
.py", line 19, in <module>
    import itertools
ImportError: No module named itertools
Error while executing Python code.
(gdb)

Please give your suggestions.

Thanks,
Sreejith

Re: Archer in Cygwin help

[Paul Pluzhnikov]

On Thu, May 21, 2009 at 10:01 AM, Sreejith <sreejithsmadhavan@gmail.com> wrote:

> (gdb) python import gdb.libstdcxx.v6.printers
> Traceback (most recent call last):
>  File "<string>", line 1, in <module>
>  File "/home/sreejith/archer/install/share/gdb/python/gdb/libstdcxx/v6/printers
> .py", line 19, in <module>
>    import itertools
> ImportError: No module named itertools
> Error while executing Python code.
> (gdb)

Please see this message and thread:
http://sources.redhat.com/ml/archer/2008-q4/msg00463.html

I think you have to either install Python in a place GDB expects it,
or set PYTHONPATH appropriately.

Cheers,
-- 
Paul Pluzhnikov

Re: Archer in Cygwin help

[Sreejith]

2009/5/22 Paul Pluzhnikov <ppluzhnikov@google.com>:
> On Thu, May 21, 2009 at 10:01 AM, Sreejith <sreejithsmadhavan@gmail.com> wrote:
>
>> (gdb) python import gdb.libstdcxx.v6.printers
>> Traceback (most recent call last):
>>  File "<string>", line 1, in <module>
>>  File "/home/sreejith/archer/install/share/gdb/python/gdb/libstdcxx/v6/printers
>> .py", line 19, in <module>
>>    import itertools
>> ImportError: No module named itertools
>> Error while executing Python code.
>> (gdb)
>
> Please see this message and thread:
> http://sources.redhat.com/ml/archer/2008-q4/msg00463.html
>
> I think you have to either install Python in a place GDB expects it,
> or set PYTHONPATH appropriately.

Thanks Paul. Before I try your suggestions, I did make install once
again for the branch:
http://sourceware.org/git/gitweb.cgi?p=archer.git;a=tree;h=refs/heads/archer-tromey-python;hb=archer-tromey-python

This time I could import gdb.libstdcxx.v6.printers which Phil
suggested. Still for STL containers, 'print' is not behaving as
expected. Please see the log:

(gdb) python print 10
10
(gdb) python import gdb.libstdcxx.v6.printers
(gdb)
(gdb) l
1       #include <list>
2
3       using namespace std;
4
5       int main()
6       {
7               list<int> myList;
8               for(int i=0; i<10; i++)
9               {
10                      myList.push_back(i);
(gdb) l
11              }
12              return 0;
13      }
14
(gdb) break 12
Breakpoint 1 at 0x401139: file list.cpp, line 12.
(gdb) run
Starting program: /cygdrive/c/eclipse/archer-build/src/a.exe
[New Thread 3912.0x172c]
[New Thread 3912.0x104c]

Breakpoint 1, main () at list.cpp:12
12              return 0;
(gdb) python print myList
Traceback (most recent call last):
  File "<string>", line 1, in <module>
NameError: name 'myList' is not defined
Error while executing Python code.
(gdb) print myList
$1 = {<_List_base<int, std::allocator<int> >> = {
    _M_impl = {<allocator<std::_List_node<int> >> =
{<new_allocator<std::_List_node<int> >> = {<No data fields>}, <No data
fields>}, _M_node = {
        _M_next = 0x682150, _M_prev = 0x6821e0}}}, <No data fields>}
(gdb)

Looks like libstdcxx.v6.printers are not known to gdb. I am wondering
how importing libstdcxx.v6.printers alone tells gdb to use new python
printers for STL. Do I need to execute some register command after
importing libstdcxx.v6.printers? Please give your suggestions.

-Sreejith

Re: Archer in Cygwin help

[Phil Muldoon]

Sreejith wrote:
> 2009/5/22 Paul Pluzhnikov <ppluzhnikov@google.com>:
>   
> (gdb) python import gdb.libstdcxx.v6.printers
> (gdb)
>   


Ok looks like the printers are loaded, that's good!


> (gdb) python print myList
> Traceback (most recent call last):
>   File "<string>", line 1, in <module>
> NameError: name 'myList' is not defined
>   

Python does not know anything about myList, it is something that is 
defined in the inferior (the program you are debugging). So the error 
message is correct from Python's point of view. At this point you should 
use:

print myList

(not: python print myList.) What happens then is the pretty-printing 
code will ask the Python pretty-printers if they have a printer 
registered that can print that variable. If so that printer is called, 
and the output is returned to GDB. GDB then formats the output and 
prints it to the screen.


Let us know how it turns out!

Regards

Phil

Re: Archer in Cygwin help

[Sreejith]

2009/5/22 Phil Muldoon <pmuldoon@redhat.com>:
> Sreejith wrote:
>>
>> 2009/5/22 Paul Pluzhnikov <ppluzhnikov@google.com>:
>>  (gdb) python import gdb.libstdcxx.v6.printers
>> (gdb)
>>
>
>
> Ok looks like the printers are loaded, that's good!
>
>
>> (gdb) python print myList
>> Traceback (most recent call last):
>>  File "<string>", line 1, in <module>
>> NameError: name 'myList' is not defined
>>
>
> Python does not know anything about myList, it is something that is defined
> in the inferior (the program you are debugging). So the error message is
> correct from Python's point of view. At this point you should use:
>
> print myList
>
> (not: python print myList.) What happens then is the pretty-printing code
> will ask the Python pretty-printers if they have a printer registered that
> can print that variable. If so that printer is called, and the output is
> returned to GDB. GDB then formats the output and prints it to the screen.

In my previous mail, I had mentioned out put of both (python print
myList and print myList). Here it is for your reference:

(gdb) print myList
$1 = {<_List_base<int, std::allocator<int> >> = {
   _M_impl = {<allocator<std::_List_node<int> >> =
{<new_allocator<std::_List_node<int> >> = {<No data fields>}, <No data
fields>}, _M_node = {
       _M_next = 0x682150, _M_prev = 0x6821e0}}}, <No data fields>}
(gdb)

From your explanation, I understand that there is no printers
registered matching the type of myList and hence gdb is using it's
'own printer'. Is that correct? Please share your thoughts.

-Sreejith

Re: Archer in Cygwin help

[Sreejith]

2009/5/22 Sreejith <sreejithsmadhavan@gmail.com>:
> 2009/5/22 Phil Muldoon <pmuldoon@redhat.com>:
>> Sreejith wrote:
>>>
>>> 2009/5/22 Paul Pluzhnikov <ppluzhnikov@google.com>:
>>>  (gdb) python import gdb.libstdcxx.v6.printers
>>> (gdb)
>>>
>>
>>
>> Ok looks like the printers are loaded, that's good!
>>
>>
>>> (gdb) python print myList
>>> Traceback (most recent call last):
>>>  File "<string>", line 1, in <module>
>>> NameError: name 'myList' is not defined
>>>
>>
>> Python does not know anything about myList, it is something that is defined
>> in the inferior (the program you are debugging). So the error message is
>> correct from Python's point of view. At this point you should use:
>>
>> print myList
>>
>> (not: python print myList.) What happens then is the pretty-printing code
>> will ask the Python pretty-printers if they have a printer registered that
>> can print that variable. If so that printer is called, and the output is
>> returned to GDB. GDB then formats the output and prints it to the screen.
>
> In my previous mail, I had mentioned out put of both (python print
> myList and print myList). Here it is for your reference:
>
> (gdb) print myList
> $1 = {<_List_base<int, std::allocator<int> >> = {
>   _M_impl = {<allocator<std::_List_node<int> >> =
> {<new_allocator<std::_List_node<int> >> = {<No data fields>}, <No data
> fields>}, _M_node = {
>       _M_next = 0x682150, _M_prev = 0x6821e0}}}, <No data fields>}
> (gdb)
>
> From your explanation, I understand that there is no printers
> registered matching the type of myList and hence gdb is using it's
> 'own printer'. Is that correct? Please share your thoughts.

The following post describes this a bit in detail.
http://tromey.com/blog/?p=524
I tried executing
gdb.libstdcxx.v6.printers.register_libstdcxx_printers(gdb.get_current_objfile())
after importing libstdcxx.v6.printers as discussed in the post. But
doesn't work as well.

-Sreejith

Re: Archer in Cygwin help

[Tom Tromey]

>>>>> "Sreejith" == Sreejith  <sreejithsmadhavan@gmail.com> writes:

Sreejith> I tried executing
Sreejith> gdb.libstdcxx.v6.printers.register_libstdcxx_printers(gdb.get_current_objfile())
Sreejith> after importing libstdcxx.v6.printers as discussed in the post. But
Sreejith> doesn't work as well.

I think that ought to work.

After doing that try:

    python print gdb.pretty_printers

Tom

Re: Archer in Cygwin help

[Sreejith]

2009/5/27 Tom Tromey <tromey@redhat.com>:
>>>>>> "Sreejith" == Sreejith  <sreejithsmadhavan@gmail.com> writes:
>
> Sreejith> I tried executing
> Sreejith> gdb.libstdcxx.v6.printers.register_libstdcxx_printers(gdb.get_current_objfile())
> Sreejith> after importing libstdcxx.v6.printers as discussed in the post. But
> Sreejith> doesn't work as well.
>
> I think that ought to work.
>
> After doing that try:
>
>    python print gdb.pretty_printers

That gives the following output:

$ ./gdb.exe ../../src/a.exe
GNU gdb (GDB) 6.8.50.20090106-cvs
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-pc-cygwin".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
(gdb) python import gdb.libstdcxx.v6.printers
(gdb) gdb.libstdcxx.v6.printers.register_libstdcxx_printers(gdb.get_current_objfile())
Undefined command: "gdb".  Try "help".
(gdb) python gdb.libstdcxx.v6.printers.register_libstdcxx_printers(gdb.get_current_objfile())
Traceback (most recent call last):
  File "<string>", line 1, in <module>
AttributeError: 'module' object has no attribute 'get_current_objfile'
Error while executing Python code.
(gdb) python print gdb.pretty_printers
[<function lookup_function at 0x7fec33ac>]
(gdb)

Is this the expected output?

Thanks,
Sreejith

Re: Archer in Cygwin help

[Tom Tromey]

>>>>> "Sreejith" == Sreejith  <sreejithsmadhavan@gmail.com> writes:

Sreejith> (gdb) python gdb.libstdcxx.v6.printers.register_libstdcxx_printers(gdb.get_current_objfile())
Sreejith> Traceback (most recent call last):
Sreejith>   File "<string>", line 1, in <module>
Sreejith> AttributeError: 'module' object has no attribute 'get_current_objfile'

It is just "current_objfile" now, we removed all the "get_" prefixes.

Sreejith> Error while executing Python code.
Sreejith> (gdb) python print gdb.pretty_printers
Sreejith> [<function lookup_function at 0x7fec33ac>]

Looks like something is working here.

Tom

Re: Archer in Cygwin help

[Sreejith]

2009/6/1 Tom Tromey <tromey@redhat.com>:
>>>>>> "Sreejith" == Sreejith  <sreejithsmadhavan@gmail.com> writes:
>
> Sreejith> (gdb) python gdb.libstdcxx.v6.printers.register_libstdcxx_printers(gdb.get_current_objfile())
> Sreejith> Traceback (most recent call last):
> Sreejith>   File "<string>", line 1, in <module>
> Sreejith> AttributeError: 'module' object has no attribute 'get_current_objfile'
>
> It is just "current_objfile" now, we removed all the "get_" prefixes.
>
> Sreejith> Error while executing Python code.
> Sreejith> (gdb) python print gdb.pretty_printers
> Sreejith> [<function lookup_function at 0x7fec33ac>]
>
> Looks like something is working here.

I tried the correction you mentioned and it executed with out any
errors. But still 'python print gdb.pretty_printers' gives same error
mentioned above. Also this is the output I get when I print myList
object:

(gdb) print myList
$1 = {<_List_base<int, std::allocator<int> >> = {
    _M_impl = {<allocator<std::_List_node<int> >> =
{<new_allocator<std::_List_node<int> >> = {<No data fields>}, <No data
fields>}, _M_node = {
        _M_next = 0x682130, _M_prev = 0x6821c0}}}, <No data fields>}
(gdb)

-Sreejith