Re: [Buildroot] [PATCH 2/2] toolchain/helpers.mk: gdbinit: set auto-load-safe-path before sysroot

[Thomas De Schampheleire <patrickdepinguin@gmail.com>]

Hi Arnout,

El mar, 21 sept 2021 a las 22:46, Arnout Vandecappelle
(<arnout@mind.be>) escribió:
>
>
>
> On 13/09/2021 09:29, Thomas De Schampheleire wrote:
> > From: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
> >
> > The gdbinit supplied by Buildroot does two things:
> > A. specify the sysroot where gdb can find shared libraries
> > B. mark the sysroot as a 'safe path' for its auto-load feature, to make sure
> >    that pretty printers for libstdc++.so are added automatically (see commit
> >    6fb3216a80c64c08375429d89497eaeec5622150)
> >
> > When debugging a core file, and the gdbinit file is specified via '-x'
> > rather than '-ix', then the order of these settings matters: If you first
> > set the sysroot, then gdb will immediately start finding the shared
> > libraries it needs for the core file, detect libstdc++ and its associated
> > libstdc++-gdb.py file, then give a big warning about safe paths:
> >
> >    warning: File ".../i686-buildroot-linux-gnu/sysroot/lib/libstdc++.so.6.0.24-gdb.py"
> >            auto-loading has been declined by your `auto-load safe-path' set
> >            to "$debugdir:$datadir/auto-load".
> >    To enable execution of this file add
> >            add-auto-load-safe-path .../i686-buildroot-linux-gnu/sysroot/lib/libstdc++.so.6.0.24-gdb.py
> >    line to your configuration file "/home/me/.gdbinit".
> >    To completely disable this security protection add
> >            set auto-load safe-path /
> >    line to your configuration file "/home/me/.gdbinit".
> >    For more information about this security protection see the
> >    "Auto-loading safe path" section in the GDB manual.  E.g., run from the shell:
> >            info "(gdb)Auto-loading safe path"
> >
> > and the pretty printing code is not loaded. This is because the second
> > line from the gdbinit file was not yet parsed at this point.
> >
> > By changing the order (first configuring the safe path, then setting the
> > sysroot), this issue does not appear and everything is as expected.
> >
> > Note that when '-ix' were used instead of '-x' to pass the gdbinit file to
> > gdb, then the order would not matter, because the entire gdbinit file would
> > be parsed before considering the core file.
> > However, even though the Buildroot manual now suggests '-ix', users may not
> > have noticed this change and continue to use '-x'.
>
>   Whaa, excellent, not content with fixing a bug once, you fix it twice!


Just to clarify: there were two sets of warnings:

1. problems loading shared libraries
2. problems with the auto-load path / pretty printers

Switching from -x to -ix solves both problems.
But if you stick with '-x', this second patch only fixes the second
problem, not the first.

Best regards,
Thomas
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