Re: How to load C++ pretty-printers

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 16 Mar 2019 10:25:43 -0400
> From: Simon Marchi <simon.marchi@polymtl.ca>
> Cc: asmwarrior <asmwarrior@gmail.com>, gdb@sourceware.org
> 
> If it can help, I have something similar to that in my .gdbinit (whereas 
> asmwarrior has put the same content in a separate file, my.gdb, which 
> they then source by hand).
> 
> When libstdc++ is linked dynamically with a program and you debug that 
> program, GDB will "auto-load" the file corresponding to the libstdc++ 
> shared library.  In my case, it's at 
> "/usr/share/gdb/auto-load/usr/lib/libstdc++.so.6.0.25-gdb.py".  This 
> file tries to find where the GCC-provided libstdc++ pretty printers are 
> installed, and adds this path to the Python import path.  It then calls 
> register_libstdcxx_printers, a function provided by the libstdc++ pretty 
> printers.
> 
> When libstdc++ is linked statically, the auto-load does not happen, as 
> you mentioned.  So the idea here is to replicate what the auto-load 
> script does, but by hand.
> 
> In my case, I have these lines to adjust the Python import path to add 
> GCC's pretty printers directory:
> 
>    python import sys
>    python sys.path.insert(0, '/usr/share/gcc-8.2.1/python')
> 
> And then I manually trigger the GDB auto-load script, that would 
> normally be sourced automatically when loading the libstdc++ shared lib:
> 
>    source /usr/share/gdb/auto-load/usr/lib/libstdc++.so.6.0.25-gdb.py

Ah, thanks, this script was the missing piece.  In the MinGW GCC
distribution it installs into lib/gcc/mingw32/VERSION/, where VERSION
is the GCC version.  The script is also named differently, due to the
MS-Windows .dll.a import library.

So, for the record, I now have this in my ~/.gdbinit

  python import sys
  python sys.path.insert(0, 'd:/usr/share/gcc-7.3.0/python')
  source d:/usr/lib/gcc/mingw32/7.3.0/libstdc++.dll.a-gdb.py

(The last line both imports the function register_libstdcxx_printers,
and calls that function.)

> The "set auto-load safe-path" line is to define it is safe to auto-load 
> things from.  If you are missing something, you should know quickly 
> enough, as GDB will print you a warning, saying it didn't auto-load X, 
> because X is not in a safe path (as well as information about how to 
> adjust it).

Yes, I already have auto-load safe-path set to not get in the way.

Thanks.