Cannot compile: error: ‘this’ pointer is null

[g3n35i5]

Describe the bug

Expected behavior: jsoncons compiles without errors.

Actual behavior: I'm getting the following error:

/tmp/jsoncons/tests/src/json_traits_macro_functional_tests.cpp: In static member function ‘static jsoncons::json_type_traits<Json, {anonymous}::ns::Employee_NCGN>::value_type jsoncons::json_type_traits<Json, {anonymous}::ns::Employee_NCGN>::as(const Json&)’:
/tmp/jsoncons/include/jsoncons/json_traits_macros.hpp:530:172: error: ‘this’ pointer is null [-Werror=nonnull]
  530 | #define JSONCONS_CTOR_GETTER_NAME_AS_LAST_2(Getter, Name) (ajson.contains(Name)) ? (ajson.at(Name)).template as<typename std::decay<decltype(((value_type*)nullptr)->Getter())>::type>() : typename std::decay<decltype(((value_type*)nullptr)->Getter())>::type()
      |                                                                                                                                              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~

Enumerate the steps to reproduce the bug

cd /tmp
git clone https://github.com/danielaparker/jsoncons.git
cd jsoncons
git checkout v0.168.1
mkdir build && cd build
cmake ..
make

What compiler, architecture, and operating system?

• Compiler: g++
• Architecture: x64
• Operating system: Archlinux

What jsoncons library version?

• Latest release 0.168.1

[danielaparker]

It appears that with the -Werror=nonnull compiler option, your compiler doesn't like to see

(value_type*)nullptr

inside a decltype specifier. I added the -Werror=nonnull option for our g++ builds, but wasn't able to reproduce this issue on any of our test environments.

While not being able to reproduce it, I changed (value_type*)nullptr to std::declval<value_type*>(), which may satisfy your compiler. Would you be able to repeat your test with the code on master, and report back with the results?

[g3n35i5]

@danielaparker works perfectly, thank you for that quick solution!