[PUSHED 6/6] gdb: print backtrace for internal error/warning

[Eli Zaretskii]

> From: Andrew Burgess <andrew.burgess@embecosm.com>
> Date: Tue, 28 Sep 2021 12:26:24 +0100
> 
>   ../../src.dev-3/gdb/maint.c:82: internal-error: blah
>   A problem internal to GDB has been detected,
>   further debugging may prove unreliable.
>   Create a core file of GDB? (y or n) n
> 
> My hope is that this backtrace might make it slightly easier to
> diagnose GDB issues if all that is provided is the console output, I
> find that we frequently get reports of an assert being hit that is
> located in pretty generic code (frame.c, value.c, etc) and it is not
> always obvious how we might have arrived at the assert.
> 
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=26377
> ---
>  gdb/NEWS                                      |   8 ++
>  gdb/doc/gdb.texinfo                           |  13 ++
>  .../gdb.base/bt-on-error-and-warning.exp      | 118 ++++++++++++++++++
>  gdb/testsuite/gdb.base/bt-on-fatal-signal.exp |  36 ------
>  gdb/utils.c                                   |  36 +++++-
>  5 files changed, 174 insertions(+), 37 deletions(-)
>  create mode 100644 gdb/testsuite/gdb.base/bt-on-error-and-warning.exp
> 
> diff --git a/gdb/NEWS b/gdb/NEWS
> index d7c29c82edb..1e25cb8cc36 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -19,6 +19,14 @@ show source open
>    to open and read source code files, which can be useful if the files
>    are located over a slow network connection.
>  
> +maint set internal-error backtrace on|off
> +maint show internal-error backtrace
> +maint set internal-warning backtrace on|off
> +maint show internal-warning backtrace
> +  GDB can now print a backtrace of itself when it encounters either an
> +  internal-error, or an internal-warning.  This is on by default for
> +  internal-error and off by default for internal-warning.

Does this depend on libbacktrace?  If so, should that be mentioned in
the documentation?

> +When @value{GDBN} reports an internal problem (error or warning) it is
> +possible to have a backtrace of @value{GDBN} printed to stderr.  This

I suggest "standard error stream" instead of "stderr".

The documentation parts are okay with these nits taken care of.
Thanks.