Compile error with GCC

[ramon-garcia]

While building the master version with GCC, the following error appeared:
In file included from /devel/bond/cpp/inc/bond/core/parser.h:8:0, from /devel/bond/cpp/inc/bond/core/apply.h:9, from /devel/bond/cpp/inc/bond/core/bond.h:7, from /devel/bond/build/cpp/bond/core/bond_apply.h:16, from /devel/bond/build/cpp/bond/core/bond_apply.cpp:13: /devel/bond/cpp/inc/bond/core/value.h: In member function ‘void bond::DeserializeElement(X&, const I&, const T&)::Deserialize::operator()(typename bond::element_type<T>::type&)’: /devel/bond/cpp/inc/bond/core/value.h:644:57: error: non-template type ‘Deserialize’ used as a template this->element.template Deserialize<Protocols>(e); ^

This looks like a limitation of GCC, though I tested it with GCC 4.9, 6.3.0 and 7.1

Attached a workaround.

fix_gcc_core_value.diff.txt

[ramon-garcia]

I confirm that this is a bug in GCC.

A testcase fails with GCC and succeeds with Clang (checked by testing in https://gcc.godbolt.org/ )

[chwarr]

Thanks for the heads up.
@ara-ayvazyan, you're C++ standards knowledge if better than mine. Do you have time to come up with a cross-compiler, cross-version fix, even if there's a bug in GCC here?

(GCC may be following the standard, and Clang and MSVC are missing this one. Or, it may very well be a bug in GCC...)

There's a bug for this in GCC's bug tracker. It looks like it was opened by @ramon-garcia.

[ara-ayvazyan]

Sure, I'll take a look.

[ara-ayvazyan]

Here is a shorter repro:

template <typename P, typename T>
void foo()
{
    struct X
    {
        void bar()
        {
            this->var.template X<P>();
        }

        T var;
    };
}

I'm not sure which compiler is correct (will need to contact some C++ language lawyer 😃), but this can be resolved by adding T:: just before the template keyword:

this->var.T::template X<P>();

Renaming the struct X is probably safer.

[ramon-garcia]

@chwarr Yes, I posted the bug in GCC bug tracker.

I couldn't figure out that the name clash between Deserialize struct and Deserialize method is the cause. In this case, renaming the struct is safe solution. Please consider this fix. Even if GCC is wrong, it is the mainstream compiler in Linux. It would take years until new releases include GCC 8 with this bug fixed.

[chwarr]

@ramon-garcia, agreed. Let me put together a PR.