Fix compile error in c++20 (#510)

In c++20, more constraints are applied:

* constructor and destructor are not allowed to have template id
* adding two enum value needs explicit convertion

src/backend/gporca/libgpopt/include/gpopt/base/CStateMachine.h

@@ -254,14 +254,10 @@ class CStateMachine
 	}
 
 public:
-	CStateMachine<TEnumState, tenumstateSentinel, TEnumEvent,
-				  tenumeventSentinel>(
-		const CStateMachine<TEnumState, tenumstateSentinel, TEnumEvent,
-							tenumeventSentinel> &) = delete;
+	CStateMachine(const CStateMachine &) = delete;
 
 	// ctor
-	CStateMachine<TEnumState, tenumstateSentinel, TEnumEvent,
-				  tenumeventSentinel>()
+	CStateMachine()
 		: m_tenumstate(TesInitial())
 	{
 		GPOS_ASSERT(0 < tenumstateSentinel && 0 < tenumeventSentinel &&

src/backend/gporca/libgpopt/include/gpopt/search/CJobStateMachine.h

@@ -95,8 +95,7 @@ class CJobStateMachine
 	CJobStateMachine(const CJobStateMachine &) = delete;
 
 	// ctor
-	CJobStateMachine<TEnumState, estSentinel, TEnumEvent, eevSentinel>() =
-		default;
+	CJobStateMachine() = default;
 
 	// dtor
 	~CJobStateMachine() = default;

src/backend/gporca/libgpopt/include/gpopt/xforms/CXform.h

@@ -25,7 +25,7 @@
 #include "naucrates/traceflags/traceflags.h"
 
 // Macro for enabling and disabling xforms
-#define GPOPT_DISABLE_XFORM_TF(x) EopttraceDisableXformBase + x
+#define GPOPT_DISABLE_XFORM_TF(x) EopttraceDisableXformBase + static_cast<int>(x)
 #define GPOPT_ENABLE_XFORM(x) GPOS_UNSET_TRACE(GPOPT_DISABLE_XFORM_TF(x))
 #define GPOPT_DISABLE_XFORM(x) GPOS_SET_TRACE(GPOPT_DISABLE_XFORM_TF(x))
 #define GPOPT_FENABLED_XFORM(x) !GPOS_FTRACE(GPOPT_DISABLE_XFORM_TF(x))

src/backend/gporca/libgpopt/include/gpopt/xforms/CXformApply2Join.h

@@ -257,7 +257,7 @@ class CXformApply2Join : public CXformExploration
 	CXformApply2Join(const CXformApply2Join &) = delete;
 
 	// ctor for deep pattern
-	explicit CXformApply2Join<TApply, TJoin>(CMemoryPool *mp, BOOL)
+	explicit CXformApply2Join(CMemoryPool *mp, BOOL)
 		:  // pattern
 		  CXformExploration(GPOS_NEW(mp) CExpression(
 			  mp, GPOS_NEW(mp) TApply(mp),
@@ -272,7 +272,7 @@ class CXformApply2Join : public CXformExploration
 	}
 
 	// ctor for shallow pattern
-	explicit CXformApply2Join<TApply, TJoin>(CMemoryPool *mp)
+	explicit CXformApply2Join(CMemoryPool *mp)
 		:  // pattern
 		  CXformExploration(GPOS_NEW(mp) CExpression(
 			  mp, GPOS_NEW(mp) TApply(mp),
@@ -287,14 +287,13 @@ class CXformApply2Join : public CXformExploration
 	}
 
 	// ctor for passed pattern
-	CXformApply2Join<TApply, TJoin>(CMemoryPool *,	// mp
-									CExpression *pexprPattern)
+	CXformApply2Join(CMemoryPool * /* mp */, CExpression *pexprPattern)
 		: CXformExploration(pexprPattern)
 	{
 	}
 
 	// dtor
-	~CXformApply2Join<TApply, TJoin>() override = default;
+	~CXformApply2Join() override = default;
 
 	// is transformation an Apply decorrelation (Apply To Join) xform?
 	BOOL

src/backend/gporca/libgpos/include/gpos/common/CAutoP.h

@@ -39,14 +39,14 @@ class CAutoP : public CStackObject
 	T *m_object;
 
 public:
-	CAutoP<T>(const CAutoP &) = delete;
+	CAutoP(const CAutoP &) = delete;
 
 	// ctor
-	explicit CAutoP<T>() : m_object(nullptr)
+	explicit CAutoP() : m_object(nullptr)
 	{
 	}
 
-	explicit CAutoP<T>(T *object) : m_object(object)
+	explicit CAutoP(T *object) : m_object(object)
 	{
 	}
 

src/backend/gporca/libgpos/include/gpos/common/CAutoRef.h

@@ -30,15 +30,15 @@ class CAutoRef : public CAutoP<T>
 {
 private:
 public:
-	CAutoRef<T>(const CAutoRef &) = delete;
+	CAutoRef(const CAutoRef &) = delete;
 
 	// ctor
-	explicit CAutoRef<T>() : CAutoP<T>()
+	explicit CAutoRef() : CAutoP<T>()
 	{
 	}
 
 	// ctor
-	explicit CAutoRef<T>(T *object) : CAutoP<T>(object)
+	explicit CAutoRef(T *object) : CAutoP<T>(object)
 	{
 	}
 

src/backend/gporca/libgpos/include/gpos/common/CAutoRg.h

@@ -34,15 +34,15 @@ class CAutoRg : public CStackObject
 	T *m_object_array;
 
 public:
-	CAutoRg<T>(const CAutoRg &) = delete;
+	CAutoRg(const CAutoRg &) = delete;
 
 	// ctor
-	explicit CAutoRg<T>() : m_object_array(nullptr)
+	explicit CAutoRg() : m_object_array(nullptr)
 	{
 	}
 
 	// ctor
-	explicit CAutoRg<T>(T *object_array) : m_object_array(object_array)
+	explicit CAutoRg(T *object_array) : m_object_array(object_array)
 	{
 	}
 

src/backend/gporca/libgpos/include/gpos/common/CDynamicPtrArray.h

@@ -145,11 +145,10 @@ class CDynamicPtrArray : public CRefCount
 	}
 
 public:
-	CDynamicPtrArray<T, CleanupFn>(const CDynamicPtrArray<T, CleanupFn> &) =
-		delete;
+	CDynamicPtrArray(const CDynamicPtrArray &) = delete;
 
 	// ctor
-	explicit CDynamicPtrArray<T, CleanupFn>(CMemoryPool *mp, ULONG min_size = 4,
+	explicit CDynamicPtrArray(CMemoryPool *mp, ULONG min_size = 4,
 											ULONG expansion_factor = 10)
 		: m_mp(mp),
 		  m_capacity(0),
@@ -165,7 +164,7 @@ class CDynamicPtrArray : public CRefCount
 	}
 
 	// dtor
-	~CDynamicPtrArray<T, CleanupFn>() override
+	~CDynamicPtrArray() override
 	{
 		Clear();
 

src/backend/gporca/libgpos/include/gpos/common/CEnumSet.h

@@ -30,22 +30,22 @@ class CEnumSet : public CBitSet
 {
 private:
 public:
-	CEnumSet<T, sentinel_index>(const CEnumSet<T, sentinel_index> &) = delete;
+	CEnumSet(const CEnumSet &) = delete;
 
 	// ctor
-	explicit CEnumSet<T, sentinel_index>(CMemoryPool *mp)
+	explicit CEnumSet(CMemoryPool *mp)
 		: CBitSet(mp, sentinel_index)
 	{
 	}
 
-	explicit CEnumSet<T, sentinel_index>(
-		CMemoryPool *mp, const CEnumSet<T, sentinel_index> &enum_set)
+	explicit CEnumSet(
+		CMemoryPool *mp, const CEnumSet &enum_set)
 		: CBitSet(mp, enum_set)
 	{
 	}
 
 	// dtor
-	~CEnumSet<T, sentinel_index>() override = default;
+	~CEnumSet() override = default;
 
 	// determine if bit is set
 	BOOL

src/backend/gporca/libgpos/include/gpos/common/CEnumSetIter.h

@@ -30,18 +30,17 @@ class CEnumSetIter : public CBitSetIter
 {
 private:
 public:
-	CEnumSetIter<T, sentinel_index>(const CEnumSetIter<T, sentinel_index> &) =
-		delete;
+	CEnumSetIter(const CEnumSetIter &) = delete;
 
 	// ctor
-	explicit CEnumSetIter<T, sentinel_index>(
+	explicit CEnumSetIter(
 		const CEnumSet<T, sentinel_index> &enum_set)
 		: CBitSetIter(enum_set)
 	{
 	}
 
 	// dtor
-	~CEnumSetIter<T, sentinel_index>() = default;
+	~CEnumSetIter() = default;
 
 	// current enum
 	T

src/backend/gporca/libgpos/include/gpos/common/CHashMap.h

@@ -177,12 +177,10 @@ class CHashMap : public CRefCount
 	}
 
 public:
-	CHashMap(const CHashMap<K, T, HashFn, EqFn, DestroyKFn, DestroyTFn> &) =
-		delete;
+	CHashMap(const CHashMap &) = delete;
 
 	// ctor
-	CHashMap<K, T, HashFn, EqFn, DestroyKFn, DestroyTFn>(CMemoryPool *mp,
-														 ULONG num_chains = 127)
+	CHashMap(CMemoryPool *mp, ULONG num_chains = 127)
 		: m_mp(mp),
 		  m_num_chains(num_chains),
 		  m_size(0),
@@ -196,7 +194,7 @@ class CHashMap : public CRefCount
 	}
 
 	// dtor
-	~CHashMap<K, T, HashFn, EqFn, DestroyKFn, DestroyTFn>() override
+	~CHashMap() override
 	{
 		// release all hash chains
 		Clear();

src/backend/gporca/libgpos/include/gpos/common/CHashMapIter.h

@@ -59,19 +59,17 @@ class CHashMapIter : public CStackObject
 	}
 
 public:
-	CHashMapIter(const CHashMapIter<K, T, HashFn, EqFn, DestroyKFn, DestroyTFn>
-					 &) = delete;
+	CHashMapIter(const CHashMapIter &) = delete;
 
 	// ctor
-	CHashMapIter<K, T, HashFn, EqFn, DestroyKFn, DestroyTFn>(TMap *ptm)
+	CHashMapIter(TMap *ptm)
 		: m_map(ptm), m_chain_idx(0), m_key_idx(0)
 	{
 		GPOS_ASSERT(nullptr != ptm);
 	}
 
 	// dtor
-	virtual ~CHashMapIter<K, T, HashFn, EqFn, DestroyKFn, DestroyTFn>() =
-		default;
+	virtual ~CHashMapIter() = default;
 
 	// advance iterator to next element
 	BOOL

src/backend/gporca/libgpos/include/gpos/common/CHashSet.h

@@ -160,10 +160,10 @@ class CHashSet : public CRefCount
 	}
 
 public:
-	CHashSet(const CHashSet<T, HashFn, EqFn, CleanupFn> &) = delete;
+	CHashSet(const CHashSet &) = delete;
 
 	// ctor
-	CHashSet<T, HashFn, EqFn, CleanupFn>(CMemoryPool *mp, ULONG size = 127)
+	CHashSet(CMemoryPool *mp, ULONG size = 127)
 		: m_mp(mp),
 		  m_num_chains(size),
 		  m_size(0),
@@ -177,7 +177,7 @@ class CHashSet : public CRefCount
 	}
 
 	// dtor
-	~CHashSet<T, HashFn, EqFn, CleanupFn>() override
+	~CHashSet() override
 	{
 		// release all hash chains
 		Clear();

src/backend/gporca/libgpos/include/gpos/common/CHashSetIter.h

@@ -35,17 +35,17 @@ class CHashSetIter : public CStackObject
 	BOOL m_is_initialized;
 
 public:
-	CHashSetIter(const CHashSetIter<T, HashFn, EqFn, CleanupFn> &) = delete;
+	CHashSetIter(const CHashSetIter &) = delete;
 
 	// ctor
-	CHashSetIter<T, HashFn, EqFn, CleanupFn>(TSet *set)
+	CHashSetIter(TSet *set)
 		: m_set(set), m_chain_idx(0), m_elem_idx(0)
 	{
 		GPOS_ASSERT(nullptr != set);
 	}
 
 	// dtor
-	virtual ~CHashSetIter<T, HashFn, EqFn, CleanupFn>() = default;
+	virtual ~CHashSetIter() = default;
 
 	// advance iterator to next element
 	BOOL

src/backend/gporca/libgpos/include/gpos/common/CStack.h

@@ -38,7 +38,7 @@ class CStack
 	CStack(CStack &) = delete;
 
 	// c'tor
-	CStack<T>(CMemoryPool *mp, ULONG min_size = 4) : m_size(0)
+	CStack(CMemoryPool *mp, ULONG min_size = 4) : m_size(0)
 	{
 		m_dynamic_ptr_array =
 			GPOS_NEW(mp) CDynamicPtrArray<T, CleanupNULL>(mp, min_size, 10);

src/backend/gporca/libgpos/include/gpos/common/CSyncHashtable.h

@@ -144,7 +144,7 @@ class CSyncHashtable
 	using DestroyEntryFuncPtr = void (*)(T *);
 
 	// ctor
-	CSyncHashtable<T, K>()
+	CSyncHashtable()
 		: m_buckets(nullptr),
 
 		  m_invalid_key(nullptr)
@@ -154,7 +154,7 @@ class CSyncHashtable
 	// dtor
 	// deallocates hashtable internals, does not destroy
 	// client objects
-	~CSyncHashtable<T, K>()
+	~CSyncHashtable()
 	{
 		Cleanup();
 	}

src/backend/gporca/libgpos/include/gpos/common/CSyncHashtableAccessByIter.h

@@ -58,11 +58,10 @@ class CSyncHashtableAccessByIter : public CSyncHashtableAccessorBase<T, K>
 	}
 
 public:
-	CSyncHashtableAccessByIter<T, K>(const CSyncHashtableAccessByIter<T, K> &) =
-		delete;
+	CSyncHashtableAccessByIter(const CSyncHashtableAccessByIter &) = delete;
 
 	// ctor
-	explicit CSyncHashtableAccessByIter<T, K>(CSyncHashtableIter<T, K> &iter)
+	explicit CSyncHashtableAccessByIter(CSyncHashtableIter<T, K> &iter)
 		: Base(iter.m_ht, iter.m_bucket_idx), m_iter(iter)
 	{
 	}

src/backend/gporca/libgpos/include/gpos/common/CSyncHashtableAccessByKey.h

@@ -68,11 +68,10 @@ class CSyncHashtableAccessByKey : public CSyncHashtableAccessorBase<T, K>
 #endif	// GPOS_DEBUG
 
 public:
-	CSyncHashtableAccessByKey<T, K>(const CSyncHashtableAccessByKey<T, K> &) =
-		delete;
+	CSyncHashtableAccessByKey(const CSyncHashtableAccessByKey &) = delete;
 
 	// ctor
-	CSyncHashtableAccessByKey<T, K>(CSyncHashtable<T, K> &ht, const K &key)
+	CSyncHashtableAccessByKey(CSyncHashtable<T, K> &ht, const K &key)
 		: Base(ht, ht.GetBucketIndex(key)), m_key(key)
 	{
 	}

src/backend/gporca/libgpos/include/gpos/common/CSyncHashtableAccessorBase.h

@@ -46,13 +46,13 @@ class CSyncHashtableAccessorBase : public CStackObject
 
 protected:
 	// ctor - protected to restrict instantiation to children
-	CSyncHashtableAccessorBase<T, K>(CSyncHashtable<T, K> &ht, ULONG bucket_idx)
+	CSyncHashtableAccessorBase(CSyncHashtable<T, K> &ht, ULONG bucket_idx)
 		: m_ht(ht), m_bucket(m_ht.GetBucket(bucket_idx))
 	{
 	}
 
 	// dtor
-	virtual ~CSyncHashtableAccessorBase<T, K>() = default;
+	virtual ~CSyncHashtableAccessorBase() = default;
 
 	// accessor to hashtable
 	CSyncHashtable<T, K> &
@@ -130,8 +130,7 @@ class CSyncHashtableAccessorBase : public CStackObject
 	}
 
 public:
-	CSyncHashtableAccessorBase<T, K>(const CSyncHashtableAccessorBase<T, K> &) =
-		delete;
+	CSyncHashtableAccessorBase(const CSyncHashtableAccessorBase &) = delete;
 
 	// unlinks element
 	void

src/backend/gporca/libgpos/include/gpos/common/CSyncHashtableIter.h

@@ -113,10 +113,10 @@ class CSyncHashtableIter
 	BOOL m_invalid_elem_inserted;
 
 public:
-	CSyncHashtableIter<T, K>(const CSyncHashtableIter<T, K> &) = delete;
+	CSyncHashtableIter(const CSyncHashtableIter &) = delete;
 
 	// ctor
-	explicit CSyncHashtableIter<T, K>(CSyncHashtable<T, K> &ht)
+	explicit CSyncHashtableIter(CSyncHashtable<T, K> &ht)
 		: m_ht(ht),
 		  m_bucket_idx(0),
 		  m_invalid_elem(nullptr),
@@ -133,7 +133,7 @@ class CSyncHashtableIter
 	}
 
 	// dtor
-	~CSyncHashtableIter<T, K>()
+	~CSyncHashtableIter()
 	{
 		if (m_invalid_elem_inserted)
 		{