On 01/10/22 17:30, Jonathan Wakely wrote:
On Sat, 1 Oct 2022 at 11:43, François Dumont <frs.dum...@gmail.com> wrote:
On 01/10/22 12:06, Jonathan Wakely wrote:
On Sat, 1 Oct 2022 at 08:20, François Dumont via Libstdc++
<libstd...@gcc.gnu.org> wrote:
I had forgotten to re-run tests after I removed the #define
_GLIBCXX_USE_CXX11_ABI 0.
The comment was misleading, it could also impact output of std::list.
I am also restoring the correct std::string alias for
std::__cxx11::basic_string, even if with my workaround it doesn't really
matter as the one for std::basic_string will be used.
I also restored the printer for std::__cxx11::string typedef. Is it
intentional to keep this ?
Yes, I kept that intentionally. There can be programs where some
objects still use that typedef, if those objects were compiled with
GCC 8.x or older.
libstdc++: Fix gdb pretty printers when dealing with std::string
Since revision 33b43b0d8cd2de722d177ef823930500948a7487 std::string
and other
similar typedef are ambiguous from a gdb point of view because it
matches both
std::basic_string<char> and std::__cxx11::basic_string<char>
symbols. For those
typedef add a workaround to accept the substitution as long as the
same regardless
of __cxx11 namespace.
Thanks for figuring out what was going wrong here, and how to fix it.
Also avoid to register printers for types in std::__cxx11::__8::
namespace, there is
no such symbols.
libstdc++-v3/ChangeLog:
* libstdc++-v3/python/libstdcxx/v6/printers.py
(Printer.add_version): Do not add
version namespace for __cxx11 symbols.
(add_one_template_type_printer): Likewise.
(add_one_type_printer): Likewise.
(FilteringTypePrinter._recognizer.recognize): Add a
workaround for std::string & al
ambiguous typedef matching both std:: and std::__cxx11::
symbols.
(register_type_printers): Refine type registration to limit
false positive in
FilteringTypePrinter._recognize.recognize requiring to look
for the type in gdb.
I don't really like this part of the change though:
I'll check what you are proposing but I don't think it is necessary to
fix the problem.
Most of my patch is an alternative way to make the filter match on
"basic_string<char", but there's also an alternative way to check for
the ambiguous string typedefs, by using match.split('::')[-1] to get
the class template name without namespaces and then compare that to
"basic_string".
I did this on my path to find out what was going wrong. Once I
understood it I consider that it was just a good change to keep. If you
think otherwise I can revert this part.
Yeah it looks like it's just an optimization to fail faster without
having to do gdb.lookup_type.
Please revert the changes to register_type_printers then, and we can
consider that part later if we want to revisit it. I'm not opposed to
making that fail-fast optimization, as long as we keep the property
that FilteringTypePrinter.match is the class template name. Maybe it
should be renamed to something other than "match" to make that clear.
Or change the doc ? For my info, why is it so important to comply to the
current doc ? Is it extracted from some gdb doc ?
Now that the problem is fixed it is less important but I never managed
to find any doc about this gdb feature that we are relying on.
The rest of the patch is OK for trunk, thanks.
I also noted that gdb consider the filters as a filo list, not fifo. And
I think that the 1st filters registered are the most extensively used. I
can propose to invert all the registration if you think it worth it.
I've not noticed any performance problems with the printers, but I
have wondered how many printers is too many. That's an interesting
observation about the order they're checked. I'll talk to some of the
GDB devs to find out if they think it's something we should worry
about. Let's not try make premature optimizations until we know if it
matters.
Yes, but with the 1st registration and so the last evaluation being
'std::string' it sounds more like a premature lowering ;-)
