DEBUG_ASSERT_PURE_FUNCTION broken with GCC9

[raitraak-rrk]

First of all, thanks for the library!

GCC9 seems to break something with the pure attribute definition. Couldn't figure out what's the issue there. Temporary workaround is to define "DEBUG_ASSERT_PURE_FUNCTION=".

build.log

[NikolausDemmel]

For the same reason type_safe fails to compile for me with gcc9. Adding -DDEBUG_ASSERT_PURE_FUNCTION= works as a workaround for me as well.

$ CXX=$HOME/.linuxbrew/opt/gcc@9/bin/g++-9 CC=$HOME/.linuxbrew/opt/gcc@9/bin/gcc-9 cmake ..
-- The C compiler identification is GNU 9.1.0
-- The CXX compiler identification is GNU 9.1.0
-- Check for working C compiler: /usr/wiss/demmeln/.linuxbrew/opt/gcc@9/bin/gcc-9
-- Check for working C compiler: /usr/wiss/demmeln/.linuxbrew/opt/gcc@9/bin/gcc-9 -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/wiss/demmeln/.linuxbrew/opt/gcc@9/bin/g++-9
-- Check for working CXX compiler: /usr/wiss/demmeln/.linuxbrew/opt/gcc@9/bin/g++-9 -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Installing debug_assert via submodule
Submodule 'external/debug_assert' (https://github.com/foonathan/debug_assert) registered for path 'external/debug_assert'
Cloning into 'external/debug_assert'...
Submodule path 'external/debug_assert': checked out '0144b6532ec80349780ffac3cf85a92d87eb7b1b'
-- Configuring done
-- Generating done
-- Build files have been written to: /storage/slurm/demmeln/dba/dbatk/foo/type_safe/build
$ make
Scanning dependencies of target type_safe_example_constrained
[  2%] Building CXX object example/CMakeFiles/type_safe_example_constrained.dir/constrained.cpp.o
In file included from /storage/slurm/demmeln/dba/dbatk/foo/type_safe/include/type_safe/detail/assert.hpp:8,
                 from /storage/slurm/demmeln/dba/dbatk/foo/type_safe/include/type_safe/constrained_type.hpp:14,
                 from /storage/slurm/demmeln/dba/dbatk/foo/type_safe/example/constrained.cpp:8:
/storage/slurm/demmeln/dba/dbatk/foo/type_safe/include/type_safe/constrained_type.hpp: In lambda function:
/storage/slurm/demmeln/dba/dbatk/foo/type_safe/external/debug_assert/debug_assert.hpp:335:72: error: expected ‘{’ before ‘noexcept’
  335 |                                             DEBUG_ASSERT_PURE_FUNCTION noexcept { return Expr; },  \
      |                                                                        ^~~~~~~~
/storage/slurm/demmeln/dba/dbatk/foo/type_safe/include/type_safe/constrained_type.hpp:397:9: note: in expansion of macro ‘DEBUG_ASSERT’
  397 |         DEBUG_ASSERT(value_, detail::precondition_error_handler{});
      |         ^~~~~~~~~~~~
/storage/slurm/demmeln/dba/dbatk/foo/type_safe/include/type_safe/constrained_type.hpp: In member function ‘type_safe::constrained_modifier<T, Constraint, Verifier>::value_type& type_safe::constrained_modifier<T, Constraint, Verifier>::get()’:
/storage/slurm/demmeln/dba/dbatk/foo/type_safe/external/debug_assert/debug_assert.hpp:335:72: error: expected ‘)’ before ‘noexcept’
  335 |                                             DEBUG_ASSERT_PURE_FUNCTION noexcept { return Expr; },  \
      |                                                                        ^~~~~~~~
/storage/slurm/demmeln/dba/dbatk/foo/type_safe/include/type_safe/constrained_type.hpp:397:9: note: in expansion of macro ‘DEBUG_ASSERT’
  397 |         DEBUG_ASSERT(value_, detail::precondition_error_handler{});
      |         ^~~~~~~~~~~~
/storage/slurm/demmeln/dba/dbatk/foo/type_safe/external/debug_assert/debug_assert.hpp:334:40: note: to match this ‘(’
  334 |         debug_assert::detail::do_assert([&]()                                                      \
      |                                        ^
/storage/slurm/demmeln/dba/dbatk/foo/type_safe/include/type_safe/constrained_type.hpp:397:9: note: in expansion of macro ‘DEBUG_ASSERT’
  397 |         DEBUG_ASSERT(value_, detail::precondition_error_handler{});
      |         ^~~~~~~~~~~~
/storage/slurm/demmeln/dba/dbatk/foo/type_safe/external/debug_assert/debug_assert.hpp: In instantiation of ‘constexpr typename debug_assert::detail::enable_if<(Handler::level != 0), debug_assert::detail::regular_void>::type debug_assert::detail::do_assert(const Expr&, const debug_assert::source_location&, const char*, Handler, Args&& ...) [with Expr = type_safe::constrained_modifier<T, Constraint, Verifier>::get() [with T = std::__cxx11::basic_string<char>; Constraint = type_safe::constraints::non_empty; Verifier = type_safe::assertion_verifier; type_safe::constrained_modifier<T, Constraint, Verifier>::value_type = std::__cxx11::basic_string<char>]::<lambda()>; Handler = type_safe::detail::precondition_error_handler; Args = {}; typename debug_assert::detail::enable_if<(Handler::level != 0), debug_assert::detail::regular_void>::type = debug_assert::detail::regular_void]’:
/storage/slurm/demmeln/dba/dbatk/foo/type_safe/include/type_safe/constrained_type.hpp:397:9:   required from ‘type_safe::constrained_modifier<T, Constraint, Verifier>::value_type& type_safe::constrained_modifier<T, Constraint, Verifier>::get() [with T = std::__cxx11::basic_string<char>; Constraint = type_safe::constraints::non_empty; Verifier = type_safe::assertion_verifier; type_safe::constrained_modifier<T, Constraint, Verifier>::value_type = std::__cxx11::basic_string<char>]’
/storage/slurm/demmeln/dba/dbatk/foo/type_safe/example/constrained.cpp:25:22:   required from here
/storage/slurm/demmeln/dba/dbatk/foo/type_safe/external/debug_assert/debug_assert.hpp:283:24: error: could not convert ‘(& expr)->type_safe::constrained_modifier<T, Constraint, Verifier>::get() [with T = std::__cxx11::basic_string<char>; Constraint = type_safe::constraints::non_empty; Verifier = type_safe::assertion_verifier; type_safe::constrained_modifier<T, Constraint, Verifier>::value_type = std::__cxx11::basic_string<char>]::<lambda()>()’ from ‘void’ to ‘bool’
  283 |             return expr() ? regular_void() :
      |                    ~~~~^~
      |                        |
      |                        void
/storage/slurm/demmeln/dba/dbatk/foo/type_safe/external/debug_assert/debug_assert.hpp:286:9: error: body of ‘constexpr’ function ‘constexpr typename debug_assert::detail::enable_if<(Handler::level != 0), debug_assert::detail::regular_void>::type debug_assert::detail::do_assert(const Expr&, const debug_assert::source_location&, const char*, Handler, Args&& ...) [with Expr = type_safe::constrained_modifier<T, Constraint, Verifier>::get() [with T = std::__cxx11::basic_string<char>; Constraint = type_safe::constraints::non_empty; Verifier = type_safe::assertion_verifier; type_safe::constrained_modifier<T, Constraint, Verifier>::value_type = std::__cxx11::basic_string<char>]::<lambda()>; Handler = type_safe::detail::precondition_error_handler; Args = {}; typename debug_assert::detail::enable_if<(Handler::level != 0), debug_assert::detail::regular_void>::type = debug_assert::detail::regular_void]’ not a return-statement
  286 |         }
      |         ^
example/CMakeFiles/type_safe_example_constrained.dir/build.make:62: recipe for target 'example/CMakeFiles/type_safe_example_constrained.dir/constrained.cpp.o' failed
make[2]: *** [example/CMakeFiles/type_safe_example_constrained.dir/constrained.cpp.o] Error 1
CMakeFiles/Makefile2:116: recipe for target 'example/CMakeFiles/type_safe_example_constrained.dir/all' failed
make[1]: *** [example/CMakeFiles/type_safe_example_constrained.dir/all] Error 2
Makefile:140: recipe for target 'all' failed
make: *** [all] Error 2

[foonathan]

Yeah, it's the same issue.

I don't have access to GCC 9, so can't fix it right now. Anyone willing to do a PR changing the macro definition from __attribute__(pure) to [[gnu::pure]] and see if that fixes it?

[raitraak-rrk]

Doesn't help.
https://godbolt.org/z/TheeeA

Says the attribute is ignored, but I cannot understand the message:
note: an attribute that appertains to a type-specifier is ignored.

[foonathan]

Oh, right, I can use godbolt. I will figure something out.

[raitraak-rrk]

Thanks mate. No rush though. Workaround is good for now.

[foonathan]

I've just decided to remove the macro.

[NikolausDemmel]

Wait, I just tested this and I'm still getting the same errors for type_safe with gcc 9 on Ubuntu 16.04:

type_safe/build (detached*)$ CXX=~/.linuxbrew/bin/g++-9 CC=~/.linuxbrew/bin/gcc-9 cmake ..
-- The C compiler identification is GNU 9.1.0
-- The CXX compiler identification is GNU 9.1.0
-- Check for working C compiler: /usr/wiss/demmeln/.linuxbrew/bin/gcc-9
-- Check for working C compiler: /usr/wiss/demmeln/.linuxbrew/bin/gcc-9 -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/wiss/demmeln/.linuxbrew/bin/g++-9
-- Check for working CXX compiler: /usr/wiss/demmeln/.linuxbrew/bin/g++-9 -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Installing debug_assert via submodule
-- Configuring done
-- Generating done
-- Build files have been written to: /usr/wiss/demmeln/slurm/dba/dbatk/external/type_safe/build
type_safe/build (detached*)$ make
Scanning dependencies of target type_safe_example_optional
[  2%] Building CXX object example/CMakeFiles/type_safe_example_optional.dir/optional.cpp.o
In file included from /usr/wiss/demmeln/slurm/dba/dbatk/external/type_safe/include/type_safe/detail/assert.hpp:8,
                 from /usr/wiss/demmeln/slurm/dba/dbatk/external/type_safe/include/type_safe/optional.hpp:12,
                 from /usr/wiss/demmeln/slurm/dba/dbatk/external/type_safe/example/optional.cpp:9:
/usr/wiss/demmeln/slurm/dba/dbatk/external/type_safe/include/type_safe/optional.hpp: In lambda function:
/usr/wiss/demmeln/slurm/dba/dbatk/external/type_safe/external/debug_assert/debug_assert.hpp:335:72: error: expected ‘{’ before ‘noexcept’
  335 |                                             DEBUG_ASSERT_PURE_FUNCTION noexcept { return Expr; },  \
      |                                                                        ^~~~~~~~
/usr/wiss/demmeln/slurm/dba/dbatk/external/type_safe/include/type_safe/optional.hpp:420:9: note: in expansion of macro ‘DEBUG_ASSERT’
  420 |         DEBUG_ASSERT(has_value(), detail::precondition_error_handler{});
      |         ^~~~~~~~~~~~
/usr/wiss/demmeln/slurm/dba/dbatk/external/type_safe/include/type_safe/optional.hpp: In member function ‘decltype (declval<type_safe::basic_optional<StoragePolicy>::storage&>().get_value()) type_safe::basic_optional<StoragePolicy>::value() &’:
/usr/wiss/demmeln/slurm/dba/dbatk/external/type_safe/external/debug_assert/debug_assert.hpp:335:72: error: expected ‘)’ before ‘noexcept’
  335 |                                             DEBUG_ASSERT_PURE_FUNCTION noexcept { return Expr; },  \
      |                                                                        ^~~~~~~~
/usr/wiss/demmeln/slurm/dba/dbatk/external/type_safe/include/type_safe/optional.hpp:420:9: note: in expansion of macro ‘DEBUG_ASSERT’

[...]

PS: Curiously, it compiles fine with gcc 9 on macOS

[NikolausDemmel]

Sorry for the noise, somehow my submodules were messed up, such that git showed the new version was checked out, but the file was actually still the old one... Reinitializing the submodules fixed it.