[Development] Proposal for Qt 5.10 platforms and configurations changes

[Thiago Macieira]

On Friday, 28 April 2017 12:50:41 -03 Mat Sutcliffe wrote:
> tldr: MSVC expects to see linker symbols for inline member functions of
> exported classes. When such a function is defined within #ifdef
> Q_COMPILER_foo (being a macro that is defined for 2017 but not 2015) this
> could mean linker errors. Unknown if this effect has actually been observed
> or is merely theoretical.

Thanks Mat.

If this is the only issue, then it's only a potential issue that will not 
affect us. There's exactly one Q_COMPILER_foo macro that is in 2017 that isn't 
in 2015:
	Q_COMPILER_CONSTEXPR

And the totality of its use in public headers, aside from the definition in 
qcompilerdetection.h, is:

- qtbase/src/corelib/thread/qbasicatomic.h

#elif defined(Q_COMPILER_ATOMICS) && (defined(Q_COMPILER_CONSTEXPR) || 
defined(Q_OS_QNX))
#  include <QtCore/qatomic_cxx11.h>

// We only support one fallback: MSVC, because even on version 2015, it lacks 
full constexpr support
#elif defined(Q_CC_MSVC)
#  include <QtCore/qatomic_msvc.h>
[...]
#if defined(Q_COMPILER_CONSTEXPR) && defined(Q_COMPILER_DEFAULT_MEMBERS) && 
defined(Q_COMPILER_DELETE_MEMBERS)
#  define QT_BASIC_ATOMIC_HAS_CONSTRUCTORS
#endif

- qtbase/src/corelib/arch/qatomic_cxx11.h

#if defined(Q_COMPILER_CONSTEXPR) && defined(Q_COMPILER_DEFAULT_MEMBERS) && 
defined(Q_COMPILER_DELETE_MEMBERS)
#  define Q_BASIC_ATOMIC_INITIALIZER(a)     { a }
#else
#  define Q_BASIC_ATOMIC_INITIALIZER(a)     { ATOMIC_VAR_INIT(a) }
#endif

- qtbase/src/corelib/global/qnamespace.h

#if defined(Q_COMPILER_CLASS_ENUM) && defined(Q_COMPILER_CONSTEXPR)
    enum class Initialization {
        Uninitialized
    };
    static constexpr Q_DECL_UNUSED Initialization Uninitialized = 
Initialization::Uninitialized;
#else
    enum Initialization {
        Uninitialized
    };
#endif

None of those affect an exported class.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center