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Commit574b091

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Add castNode(type, ptr) for safe casting between NodeTag based types.
The new function allows to cast from one NodeTag based type toanother, while asserting that the conversion is valid. This replacesthe common pattern of doing a cast and a Assert(IsA(ptr, type))close-by.As this seems likely to be used pervasively, we decided to backpatchthis change the addition of this macro. Otherwise backpatched fixesare more likely not to work on back-branches.On branches before 9.6, where we do not yet rely on inline functionsbeing available, the type assertion is only performed if PG_USE_INLINEsupport is detected. The cast obviously is performed regardless.For the benefit of verifying the macro compiles in the back-branches,this commit contains a single use of the new macro. On master, asomewhat larger conversion will be committed separately.Author: Peter Eisentraut and Andres FreundReviewed-By: Tom LaneDiscussion:https://postgr.es/m/c5d387d9-3440-f5e0-f9d4-71d53b9fbe52@2ndquadrant.comBackpatch: 9.2-
1 parent56b42a3 commit574b091

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2 files changed

+21
-1
lines changed

2 files changed

+21
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lines changed

‎src/backend/tcop/postgres.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -844,7 +844,7 @@ pg_plan_queries(List *querytrees, int cursorOptions, ParamListInfo boundParams)
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foreach(query_list,querytrees)
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{
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Query*query= (Query*)lfirst(query_list);
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Query*query=castNode(Query,lfirst(query_list));
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Node*stmt;
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if (query->commandType==CMD_UTILITY)

‎src/include/nodes/nodes.h

Lines changed: 20 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -542,6 +542,26 @@ extern PGDLLIMPORT Node *newNodeMacroHolder;
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#defineIsA(nodeptr,_type_)(nodeTag(nodeptr) == T_##_type_)
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/*
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* castNode(type, ptr) casts ptr to type and, if cassert is enabled, verifies
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* that the the c actually has the appropriate type (using it's nodeTag()).
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*
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* Use an inline function when assertions are enabled, to avoid multiple
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* evaluations of the ptr argument (which could e.g. be a function call).
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*/
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#ifdefUSE_ASSERT_CHECKING
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staticinlineNode*
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castNodeImpl(enumNodeTagtype,void*ptr)
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{
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Assert(ptr==NULL||nodeTag(ptr)==type);
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returnptr;
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}
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#definecastNode(_type_,nodeptr) ((_type_ *) castNodeImpl(T_##_type_, nodeptr))
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#else
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#definecastNode(_type_,nodeptr) ((_type_ *)(nodeptr))
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#endif
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/* ----------------------------------------------------------------
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* extern declarations follow
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* ----------------------------------------------------------------

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