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

[Bruno Larsen <blarsen@redhat.com>]

On 07/11/2022 16:53, Simon Marchi via Gdb-patches wrote:
> I noticed this crash:
>
>      $ ./gdb --data-directory=data-directory -nx -q \
>            testsuite/outputs/gdb.python/pretty-print-call-by-hand/pretty-print-call-by-hand \
> 	  -x testsuite/outputs/gdb.python/pretty-print-call-by-hand/pretty-print-call-by-hand.py \
> 	  -ex "b g" -ex r
>      (gdb) info frame
>      Stack level 0, frame at 0x7fffffffdd80:
>       rip = 0x555555555160 in g
>          (/home/simark/src/binutils-gdb/gdb/testsuite/gdb.python/pretty-print-call-by-hand.c:41); saved rip = 0x5555555551a3
>       called by frame at 0x7fffffffdda0
>       source language c.
>       Arglist at 0x7fffffffdd70, args: mt=mytype is 0x555555556004 "hello world",
>          depth=10
>
>      Fatal signal: Segmentation fault
>
> This is another case of frame_info being invalidated under a function's
> feet.  The stack trace when the frame_info get invalidated looks like:
>
>      ... many frames to pretty print the arg, that eventually invalidate the frame_infos ...
>      #35 0x00005568d0a8ab24 in print_frame_arg (fp_opts=..., arg=0x7ffc3216bcb0) at /home/simark/src/binutils-gdb/gdb/stack.c:489
>      #36 0x00005568d0a8cc75 in print_frame_args (fp_opts=..., func=0x621000233210, frame=..., num=-1, stream=0x60b000000300)
>          at /home/simark/src/binutils-gdb/gdb/stack.c:898
>      #37 0x00005568d0a9536d in info_frame_command_core (fi=..., selected_frame_p=true) at /home/simark/src/binutils-gdb/gdb/stack.c:1682
>
> print_frame_args knows that print_frame_arg can invalidate frame_info
> objects, and therefore calls prepare_reinflate/reinflate.  However,
> info_frame_command_core has a separate frame_info_ptr instance (it is
> passed by value / copy).  So info_frame_command_core needs to know that
> print_frame_args can invalidate frame_info objects, and therefore needs
> to prepare_reinflate/reinflate as well.  Add those calls, and enhance
> the gdb.python/pretty-print-call-by-hand.exp test to test that command.

Can confirm that the crash is reproducible and that the patch fixes the 
problem. Sorry for missing it the first time. Makes me wonder if I also 
missed this in print_frame... Either way:

Reviewed-By: Bruno Larsen <blarsen@redhat.com>

-- 
Cheers,
Bruno