Deprecated declarations warnings

[aldanor]

I'm compiling an empty module with -Wall with the latest pybind11 (82ece94, Linux / GCC 5.2 / both C++11 and C++14) and I get a ton of deprecated declarations warnings:

In file included from ../include/pybind11/cast.h:13:0,
 from ../include/pybind11/attr.h:13,
 from ../include/pybind11/pybind11.h:36,
 from test_module.cpp:10:
../include/pybind11/pytypes.h:190:7: warning: ‘pybind11::object::borrowed’ is deprecated: Use of the `borrowed` static variable is deprecated; use `borrowed_t{}' instead [-Wdeprecated-declarations]
 class object : public handle {
 ^
../include/pybind11/pytypes.h:241:33: note: declared here
 static constexpr borrowed_t borrowed{};
 ^
../include/pybind11/pytypes.h:190:7: warning: ‘pybind11::object::stolen’ is deprecated: Use of the `stolen` static variable is deprecated; use `stolen_t{}' instead [-Wdeprecated-declarations]
 class object : public handle {
 ^
../include/pybind11/pytypes.h:243:31: note: declared here
 static constexpr stolen_t stolen{};
 ^
../include/pybind11/pytypes.h:190:7: warning: ‘pybind11::object::borrowed’ is deprecated: Use of the `borrowed` static variable is deprecated; use `borrowed_t{}' instead [-Wdeprecated-declarations]
 class object : public handle {
 ^
../include/pybind11/pytypes.h:241:33: note: declared here
 static constexpr borrowed_t borrowed{};
 ^
../include/pybind11/pytypes.h:190:7: warning: ‘pybind11::object::stolen’ is deprecated: Use of the `stolen` static variable is deprecated; use `stolen_t{}' instead [-Wdeprecated-declarations]
 class object : public handle {
 ^
../include/pybind11/pytypes.h:243:31: note: declared here
 static constexpr stolen_t stolen{};

Source:

#include <pybind11/pybind11.h>

PYBIND11_PLUGIN(test_warnings) { return pybind11::module("test_warnings").ptr(); }

[aldanor]

(same when just running the test suite)

[jagerman]

Smells like a gcc 5 bug. Is this on plain master?

[aldanor]

Yep, just did a clean clone to double check. Plain master with -Wall -Wextra.

[aldanor]

(Oh, -Wall -Wextra is the default; so just the defaults then really)

[aldanor]

Just compiled it with GCC 4.8, no warnings.

[wojdyr]

I get the same warnings with GCC 6.2

[ 3%] Building CXX object tests/CMakeFiles/pybind11_tests.dir/test_callbacks.cpp.o
cd /home/wojdyr/fresh/pybind11/build/tests && /usr/bin/g++-6 -Dpybind11_tests_EXPORTS -I/home/wojdyr/fresh/pybind11/include -I/usr/include/python2.7 -Os -DNDEBUG -fPIC -std=c++14 -flto -fno-fat-lto-objects -fvisibility=hidden -Wall -Wextra -Wconversion -Wcast-qual -o CMakeFiles/pybind11_tests.dir/test_callbacks.cpp.o -c /home/wojdyr/fresh/pybind11/tests/test_callbacks.cpp
In file included from /home/wojdyr/fresh/pybind11/include/pybind11/cast.h:13:0,
 from /home/wojdyr/fresh/pybind11/include/pybind11/attr.h:13,
 from /home/wojdyr/fresh/pybind11/include/pybind11/pybind11.h:36,
 from /home/wojdyr/fresh/pybind11/tests/pybind11_tests.h:2,
 from /home/wojdyr/fresh/pybind11/tests/test_callbacks.cpp:10:
/home/wojdyr/fresh/pybind11/include/pybind11/pytypes.h:190:7: warning: ‘pybind11::object::borrowed’ is deprecated: Use of the `borrowed` static variable is deprecated; use `borrowed_t{}' instead [-Wdeprecated-declarations]
 class object : public handle {
 ^~~~~~
/home/wojdyr/fresh/pybind11/include/pybind11/pytypes.h:241:33: note: declared here
 static constexpr borrowed_t borrowed{};
 ^~~~~~~~
/home/wojdyr/fresh/pybind11/include/pybind11/pytypes.h:190:7: warning: ‘pybind11::object::stolen’ is deprecated: Use of the `stolen` static variable is deprecated; use `stolen_t{}' instead [-Wdeprecated-declarations]
 class object : public handle {
 ^~~~~~
/home/wojdyr/fresh/pybind11/include/pybind11/pytypes.h:243:31: note: declared here
 static constexpr stolen_t stolen{};
 ^~~~~~

[jagerman]

The warning seems to be fixed in g++ 6.3, but I could reproduce it with a Ubuntu 16.04 docker image.

We can drop the deprecated tags (or even drop them conditionally on GCC < 6.3), but I wonder if it wouldn't be easier to just drop the variables entirely. They are protected, after all, so the only potential backwards compatibility issue would be someone inheriting from object (or one of the various object descendants) in an extra-pybind11 class and using them. That seems fairly obscure to me--obscure enough to drop it. @wjakob @dean0x7d thoughts?

[wjakob]

I'm okay with deleting them.

[dean0x7d]

I'm in favor of removing the variables completely since the bug does affect all GCC versions from 5.1 to 6.2. It's a breaking change but should affect very few people and it's a quick fix: borrowed -> borrowed_t{} and stolen -> stolen_t{}.

That said, heads up to @SylvainCorlay and @JohanMabille, as it looks like xtensor-python is affected. Note that making the change to the _t{} variant is backward compatible with pybind11 2.1 and 2.0, so it's a harmless change.

[SylvainCorlay]

Thanks for the heads up!
We will move to the _t variants right away to be forward compatible.

[JohanMabille]

@SylvainCorlay you beat me to it!
@dean0x7d thanks for pinging us.

[jagerman]

Not quite as unlikely as I'd anticipated then. Still, it's good: there's a potential for linkage failures with debug builds with it.

[jagerman]

They're gone now, and the deprecation warnings with them.