Re: [PATCH] gdb: Remove support for old mangling schemes

[Keith Seitz <keiths at redhat dot com>]

On 1/8/19 3:22 PM, Simon Marchi wrote:
> An upcoming sync with gcc's libiberty [1] will remove support for old
> mangling schemes (GNU v2, Lucid, ARM, HP and EDG).  It will remove the
> cplus_demangle_opname function, so we need to get rid of its usages in
> GDB (it's a GNU v2 specific function).

Thank you so much for doing this. I was working on my own version of this
before other work got in the way.

Your patch looks just about identical to mine, and I had a few additional
questions about my own patch that I needed to answer.

I would think this should have/deserve doc and NEWS changes.

The manual talks about several demangling-related features which
raised questions for me about the general support for gnu-v2 code. If
libiberty is removing support for v2 demangling, how useful will GDB be
without the ability to demangle v2 symbols? Should we deprecate or remove
that, too? /me opens can of worms

WRT docs specifically, "set cp-abi" and "set demangling-style" still carry
either direct or indirect mentions of the different ABIs/mangling schemes in
the documentation that are now no longer valid, e.g., "lucid" and "arm".
Some comments in demangle.c do, too.

The help system references that exist today/right now, I presume, will disappear
when the libiberty patch goes back in (when libiberty_demanglers is updated), so
I *think* there's nothing to do there. 

Now the bonus. :-)

> diff --git a/gdb/testsuite/gdb.cp/demangle.exp b/gdb/testsuite/gdb.cp/demangle.exp
> index 698231b82b4..9231b54f787 100644
> --- a/gdb/testsuite/gdb.cp/demangle.exp
> +++ b/gdb/testsuite/gdb.cp/demangle.exp
> -
> -
>  proc catch_demangling_errors {command} {
>      if {[catch $command result]} {
>  	puts "ERROR: demangle.exp: while running $command: $result"
> @@ -1593,10 +183,7 @@ proc do_tests {} {
>      # Using catch_demangling_errors this way ensures that, if one of
>      # the functions raises a Tcl error, then it'll get reported, and
>      # the rest of the functions will still run.
> -    catch_demangling_errors test_lucid_style_demangling
> -    catch_demangling_errors test_gnu_style_demangling
> -    catch_demangling_errors test_arm_style_demangling
> -    catch_demangling_errors test_hp_style_demangling
> +    catch_demangling_errors test_gnuv3_style_demangling
>  

Please consider getting rid of catch_demangling_errors and removing the
"error" calls in set_demangling_style. They are not needed, and in fact,
they cause the test suite to hang if that error is ever called. I ran
across this while prepping my patch, and planned to remove it.

Of course, this (nit) is sorta orthogonal, so please feel free to ask me to do it!
;-)

Keith