On Thu, Feb 5, 2026 at 12:07 PM Jonathan Wakely <[email protected]> wrote:
> On Thu, 5 Feb 2026 at 10:52, Tomasz Kaminski <[email protected]> wrote: > > > > > > > > On Thu, Feb 5, 2026 at 11:41 AM Jonathan Wakely <[email protected]> > wrote: > >> > >> This pretty printer was updated for GCC 16 to match a change to > >> std::atomic<shared_ptr<T>>. But the gdb.Type.is_scalar property was > >> added in GDB 12.1, so we get an error for older GDB versions. > >> > >> This adds a workaround for older GDB versions. The gdb.Type.tag property > >> is None for scalar types, and should always be defined for the > >> std::atomic class template. Another option would be to use the > >> is_specialization_of function defined in printers.py, but just checking > >> for the tag is simpler. > >> > >> libstdc++-v3/ChangeLog: > >> > >> * python/libstdcxx/v6/printers.py (SharedPointerPrinter): Only > >> use gdb.Type.is_scalar if supported. > >> --- > >> > >> Tested x86_64-linux, using both GDB 8 and GDB 16, and also tested a > >> binary with the GCC 15 std::atomic<shared_ptr> can be printed by the GCC > >> 16 printers.py. > > > > I am confused about the configuration that this is aiming to address? > Someone > > having a GCC 16 installation (so they pick up new pretty-printers), but > using > > GDB-8 to debug the produced binary? > > Right. > > > Why would we put effort into supporting > > this? > > Because RHEL 8 comes with GDB 8.2 > I still do not follow up. RHEL 8 comes with GDB 8 and I assume GCC 8, certainly not 16. So someone installed GCC 16, and built the program, and we cannot require them to use and install and use GDB 16 to debug that? They already stepped out of defaults. > > > > > Outside of that patch LGTM. > > > >> libstdc++-v3/python/libstdcxx/v6/printers.py | 10 ++++++++-- > >> 1 file changed, 8 insertions(+), 2 deletions(-) > >> > >> diff --git a/libstdc++-v3/python/libstdcxx/v6/printers.py > b/libstdc++-v3/python/libstdcxx/v6/printers.py > >> index 8bb7dd2ad600..be7e7a256065 100644 > >> --- a/libstdc++-v3/python/libstdcxx/v6/printers.py > >> +++ b/libstdc++-v3/python/libstdcxx/v6/printers.py > >> @@ -292,9 +292,15 @@ class SharedPointerPrinter(printer_base): > >> if self._typename == 'std::atomic': > >> # A tagged pointer is stored as uintptr_t. > >> val = self._val['_M_refcount']['_M_val'] > >> - if val.type.is_scalar: # GCC 16 stores uintptr_t > >> + # GCC 16 stores it directly as uintptr_t > >> + # GCC 12-15 stores std::atomic<uintptr_t> > >> + if hasattr(val.type, 'is_scalar'): # Added in GDB 12.1 > >> + val_is_uintptr = val.type.is_scalar > >> + else: > >> + val_is_uintptr = val.type.tag is None > >> + if val_is_uintptr: > >> ptr_val = val > >> - else: # GCC 12-15 stores std::atomic<uintptr_t> > >> + else: > >> ptr_val = val['_M_i'] > >> ptr_val = ptr_val - (ptr_val % 2) # clear lock bit > >> ptr_type = find_type(self._val['_M_refcount'].type, > 'pointer') > >> -- > >> 2.52.0 > >> > >
