Re: [PATCH 2/7] gdb: add prepare_reinflate/reinflate around print_frame_args in info_frame_command_core

[Tom Tromey <tom@tromey.com>]

>>>>> "Simon" == Simon Marchi via Gdb-patches <gdb-patches@sourceware.org> writes:

Simon> But this shows how the current frame_info_ptr is error-prone: you have
Simon> two know which functions can, deep down their call tree, reinit the
Simon> frame cache.  And all their callers that have a frame_info_ptr object,
Simon> recursively, must explicitly do prepare_reinflate / reinflate to protect
Simon> themselves against their frame_info object being invalidated.  It's very
Simon> easy to forget some spots.

Yeah.  This problem already existed, and the rationale behind
frame_info_ptr wasn't to fix it, but rather to expose it when it happens
-- by crashing rather than allowing a UAF.

Simon> I'm currently working on making frame_info_ptr work automatically,
Simon> meaning it would grab the wrapped frame id automatically on
Simon> construction, and reinflate the frame automatically if needed

We tried this a bit, but the problem we hit was that computing the
frame id require unwinding a bit, and since the code generally uses
frame_info_ptr everywhere, gdb would end up unwinding everything.

If this can be overcome then that would be great.

Tom