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Deprecate Unused, use C++17 [[maybe_unused]] instead #4266

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Merged
dzenanz merged 2 commits into from
Nov 8, 2023
Merged

Deprecate Unused, use C++17 [[maybe_unused]] instead #4266

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0d8d4de
STYLE: Replace `Unused` calls with C++17 `[[maybe_unused]]` attribute
N-Dekker Oct 23, 2023
a24573a
STYLE: Deprecate (ITK_FUTURE_LEGACY_REMOVE) `Unused(const T &)`
N-Dekker Oct 23, 2023
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10 changes: 6 additions & 4 deletions Modules/Core/Common/include/itkSingleton.h
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Original file line number Diff line number Diff line change
Expand Up @@ -23,15 +23,18 @@
#include <map>
#include <functional>

#ifndef ITK_FUTURE_LEGACY_REMOVE
/** \brief A function which does nothing
* \deprecated Preferably use the C++ `[[maybe_unused]]` attribute instead!
*
* This function is to be used to mark parameters as unused to suppress
* compiler warning. It can be used when the parameter needs to be named
* (i.e. itkNotUsed cannot be used) but is not always used.
*/
template <typename T>
inline void
[[deprecated("Preferably use the C++ `[[maybe_unused]]` attribute instead!")]] inline void
Unused(const T &){};
#endif

namespace itk
{
Expand Down Expand Up @@ -124,9 +127,8 @@ template <typename T>
T *
Singleton(const char * globalName, std::function<void()> deleteFunc)
{
static SingletonIndex * singletonIndex = SingletonIndex::GetInstance();
Unused(singletonIndex);
T * instance = SingletonIndex::GetInstance()->GetGlobalInstance<T>(globalName);
[[maybe_unused]] static SingletonIndex * singletonIndex = SingletonIndex::GetInstance();
T * instance = SingletonIndex::GetInstance()->GetGlobalInstance<T>(globalName);
if (instance == nullptr)
{
instance = new T;
Expand Down
3 changes: 1 addition & 2 deletions Modules/Core/Common/src/itkObjectFactoryBase.cxx
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Expand Up @@ -832,8 +832,7 @@ ObjectFactoryBase::SynchronizeObjectFactoryBase(void * objectFactoryBasePrivate)
std::list<ObjectFactoryBase *>
ObjectFactoryBase::GetRegisteredFactories()
{
// static SingletonIndex * singletonIndex = SingletonIndex::GetInstance();
// Unused(singletonIndex);
// [[maybe_unused]] static SingletonIndex * singletonIndex = SingletonIndex::GetInstance();
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@N-Dekker N-Dekker Oct 23, 2023

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This commented-out declaration of singletonIndex was introduced with pull request #118 commit a66337e "ENH: Synchronize factories across modules in Python", Francois Budin (@fbudin69500), February 2019:

ITK/Modules/Core/Common/src/itkObjectFactoryBase.cxx

Lines 925 to 926 in a66337e

// static SingletonIndex * singletonIndex = SingletonIndex::GetInstance();
// Unused(singletonIndex);

Maybe we might as well just remove those two commented-out lines of code. It's very hard to keep commented-out code up-to-date. What do you think?

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@dzenanz dzenanz Oct 23, 2023

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Since you already did the work, perhaps let's keep it this time. But yes, we can occasionally clean up commented-out code.

ObjectFactoryBase::Initialize();
return m_PimplGlobals->m_RegisteredFactories;
}
Expand Down