Debugger: use gdb python pretty printer for the libstdcxx under msys2

[ollydbg]

Hi, this is my way to use gdb python pretty printer for the libstdcxx under msys2.
Suppose you use 64bit gcc compiler. My msys2 is installed under F:\msys64

In the Menu->Settings->Debugger settings. Open the debugger plugin setting dialog.

Then, in the "Executable path" field, select "F:\msys64\mingw64\bin\gdb.exe"
in the "Debugger initialization commands" field, put the following text in the edit control.

Code

source F:\msys64\mingw64\etc\gdbinit

I see that I have to modify the file "F:\msys64\mingw64\etc\gdbinit" file: below is the original code

Code

python
import sys
sys.path.insert(0, sys.path[0] + '/../../gcc-9.2.0/python')
from libstdcxx.v6.printers import register_libstdcxx_printers
end

But you have to add one line before the "end" statement like below to let the register_libstdcxx_printers function get executed.

Code

python
import sys
sys.path.insert(0, sys.path[0] + '/../../gcc-9.2.0/python')
from libstdcxx.v6.printers import register_libstdcxx_printers
register_libstdcxx_printers(None)
end

BTW: It is the same thing to add the python pretty printer for wxWidgets. You can use this file:

Code

https://github.com/wxWidgets/wxWidgets/blob/master/misc/gdb/print.py

[BlueHazzard]

a wiki article would be nice

[ollydbg]

a wiki article would be nice

Done, see here: Configure GDB pretty printer for Msys2 - CodeBlocks

Though a bit late.

[BlueHazzard]

Great!

[Suryavarman]

It doesn't work for the wx print.
When i find some time i will use "source -p" like wxWidgets team say:

this file is meant to
#               be sourced from gdb using "source -p" (or, better, autoloaded
#               in the future...)

[ollydbg]

It doesn't work for the wx print.
When i find some time i will use "source -p" like wxWidgets team say:

this file is meant to
#               be sourced from gdb using "source -p" (or, better, autoloaded
#               in the future...)

OK, I understand your problem. Here is the method to solve this problem.

First, you download the file

Code

https://github.com/wxWidgets/wxWidgets/blob/master/misc/gdb/print.py

For me, I renamed this file to wxprint.py, and I saved it to the same folder as the gdbinit file locates.

Then, I modify the gdbinit file as below:

Code

python
import sys
sys.path.insert(0, sys.path[0] + '/../../gcc-10.2.0/python')
from libstdcxx.v6.printers import register_libstdcxx_printers
register_libstdcxx_printers (None)

sys.path.insert(0, sys.path[0] + '/../../../etc')
import wxprint
end

Look at the two lines:

Code

sys.path.insert(0, sys.path[0] + '/../../../etc')
import wxprint

The first line adds the current directory of the wxprint.py, and the second line just imports the wxprint.py file. I think the "import" directive us just like the "source" directive in Python, am I correct?

Anyway, this works OK in my msys2. I can have both wxWidgets and C++ std library's pretty printers working when debugging.

BTW: I haven't find a simple way to load the wxprint.py file, I just want to avoid the first line, but that line is always needed .  Maybe, some guys can improve the loading code.

[Suryavarman]

It's works. Thank you BlueHazzard 

[ollydbg]

This is further simplified config when using msys2 based gdb. We can use the macro variables

For the gdb.exe path, just use this string:

Code

$(TARGET_COMPILER_DIR)bin\gdb.exe

and to use the gdb initialization script, use this string:

Code

source $(TARGET_COMPILER_DIR)etc\gdbinit

See the image shot below:

This make C::B more portable

[AndrewCot]

ollydbg. Thanks for the Page and info as I was able to get the wxwidget pretty printing to work with the help form the page. I fell into a few minor holes, which could filed in by updating the page so other people do not fall into the same holes, which are/were:
1) In the Menu->Settings->Debugger settings. Open the debugger plugin setting dialog and uncheck the "Disable startup scripts (-nx) (GDB only)" option.

2) If you are using the https://github.com/wxWidgets/wxWidgets/blob/master/misc/gdb/print.py file then add the following to the gdbinit file:
sys.path.insert(0, 'D:/temp')         
from wxprint import register_wxwidgets_printers
register_wxwidgets_printers (None)
Rember to change the directory to where you have saved the print.py file.

3) Update it to change the "source F:\msys64\mingw64\etc\gdbinit" to "source $(TARGET_COMPILER_DIR)etc\gdbinit"

4) You may want to change the note about the "register_libstdcxx_printers(None)" additional line was added to MSYS in https://github.com/msys2/MINGW-packages/pull/6351 (6-Apr-2020) and if people are using a later version then they do not need to do anything.

[ollydbg]

Hi, thanks for the response!

ollydbg. Thanks for the Page and info as I was able to get the wxwidget pretty printing to work with the help form the page. I fell into a few minor holes, which could filed in by updating the page so other people do not fall into the same holes, which are/were:
1) In the Menu->Settings->Debugger settings. Open the debugger plugin setting dialog and uncheck the "Disable startup scripts (-nx) (GDB only)" option.

I think this option should be "checked on", I mean we don't need the startup scripts.

2) If you are using the https://github.com/wxWidgets/wxWidgets/blob/master/misc/gdb/print.py file then add the following to the gdbinit file:
sys.path.insert(0, 'D:/temp')         
from wxprint import register_wxwidgets_printers
register_wxwidgets_printers (None)
Rember to change the directory to where you have saved the print.py file.

I don't do like that, I just shows what I did in this post:
Re: Debugger: use gdb python pretty printer for the libstdcxx under msys2
You don't need the "hard-coded path" in those settings.

3) Update it to change the "source F:\msys64\mingw64\etc\gdbinit" to "source $(TARGET_COMPILER_DIR)etc\gdbinit"

This is correct, I also do like this.

4) You may want to change the note about the "register_libstdcxx_printers(None)" additional line was added to MSYS in https://github.com/msys2/MINGW-packages/pull/6351 (6-Apr-2020) and if people are using a later version then they do not need to do anything.

Yes, I think msys2 already has configured the pretty printer for the libstdcxx library, what we need is to add some codes to the "gdbinit" file which support the wx's pretty printer.

[AndrewCot]

Feedback on feedback:
1). "Disable startup scripts (-nx) (GDB only)" option.

In the Menu->Settings->Debugger settings. Open the debugger plugin setting dialog and uncheck the "Disable startup scripts (-nx) (GDB only)" option.
>> I think this option should be "checked on", I mean we don't need the startup scripts.

If I leave the option checked [X] then the pretty printer does not work and the watch looks like it does when no pretty printer is defined for wxWidget. If uncheck [ ] the option then the GDB pretty printer watch displays a wxString in a human read able format. See attachment showing this.

2.gdbinit file:

If you are using the https://github.com/wxWidgets/wxWidgets/blob/master/misc/gdb/print.py file then add the following to the gdbinit file:
    sys.path.insert(0, 'D:/temp')         
    from wxprint import register_wxwidgets_printers
    register_wxwidgets_printers (None)
    Rember to change the directory to where you have saved the print.py file.

>>I don't do like that, I just shows what I did in this post:
>>Re: Debugger: use gdb python pretty printer for the libstdcxx under msys2
>>You don't need the "hard-coded path" in those settings.

I think the page still needs an update to add the info so someone does not need to find in the forum post (like I had to do as it did not work due to item 1), but I also had to get the syntax correct in the gdbinit):
a) Copy the https://github.com/wxWidgets/wxWidgets/blob/master/misc/gdb/print.py into :
      Linux: /etc    (checked on Linux Mint 20.1 Virtual machine)
      Windows - MSYS2: x:\msys64\mingw64\etc or x:\msys64\mingw32\etc where x: is the drive you installed Msys2 onto and depending on if you are using the 32 or 64 bit compiler
      Windows - Cygwin: - Looks like it supports pretty printing, but by default no gdbinit file exists.
      Windows - Mingw64: TBA
      MacOSx: TBA
a) Add the following to gdbinit  in the directory in the step above:

Code

sys.path.insert(0, sys.path[0] + '/../../../etc')
import wxprint