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Commitaad1617

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Silence uninitialized-value warnings in compareJsonbContainers().
Because not every path through JsonbIteratorNext() sets val->type,some compilers complain that compareJsonbContainers() is comparingpossibly-uninitialized values. The paths that don't set it returnWJB_DONE, WJB_END_ARRAY, or WJB_END_OBJECT, so it's clear bymanual inspection that the "(ra == rb)" code path is safe, andindeed we aren't seeing warnings about that. But the (ra != rb)case is much less obviously safe. In Assert-enabled builds itseems that the asserts rejecting WJB_END_ARRAY and WJB_END_OBJECTpersuade gcc 15.x not to warn, which makes little sense becauseit's impossible to believe that the compiler can prove of itsown accord that ra/rb aren't WJB_DONE here. (In fact they neverwill be, so the code isn't wrong, but why is there no warning?)Without Asserts, the appearance of warnings is quite unsurprising.We discussed fixing this by converting those two Asserts intopg_assume, but that seems not very satisfactory when it's so unclearwhy the compiler is or isn't warning: the warning could easilyreappear with some other compiler version. Let's fix it in a lessmagical, more future-proof way by changing JsonbIteratorNext()so that it always does set val->type. The cost of that should bepretty negligible, and it makes the function's API spec less squishy.Reported-by: Erik Rijkers <er@xs4all.nl>Author: Tom Lane <tgl@sss.pgh.pa.us>Reviewed-by: Andres Freund <andres@anarazel.de>Discussion:https://postgr.es/m/988bf1bc-3f1f-99f3-bf98-222f1cd9dc5e@xs4all.nlDiscussion:https://postgr.es/m/0c623e8a204187b87b4736792398eaf1@postgrespro.ruBackpatch-through: 13
1 parent8ffd9ac commitaad1617

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‎src/backend/utils/adt/jsonb_util.c

Lines changed: 14 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -277,9 +277,6 @@ compareJsonbContainers(JsonbContainer *a, JsonbContainer *b)
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else
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{
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/*
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* It's safe to assume that the types differed, and that the va
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* and vb values passed were set.
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*
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* If the two values were of the same container type, then there'd
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* have been a chance to observe the variation in the number of
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* elements/pairs (when processing WJB_BEGIN_OBJECT, say). They're
@@ -852,15 +849,20 @@ JsonbIteratorInit(JsonbContainer *container)
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* It is our job to expand the jbvBinary representation without bothering them
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* with it. However, clients should not take it upon themselves to touch array
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* or Object element/pair buffers, since their element/pair pointers are
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* garbage. Also, *val will not be set when returning WJB_END_ARRAY or
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* WJB_END_OBJECT, on the assumption that it's only useful to access values
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* when recursing in.
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* garbage.
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*
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* *val is not meaningful when the result is WJB_DONE, WJB_END_ARRAY or
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* WJB_END_OBJECT. However, we set val->type = jbvNull in those cases,
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* so that callers may assume that val->type is always well-defined.
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*/
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JsonbIteratorToken
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JsonbIteratorNext(JsonbIterator**it,JsonbValue*val,boolskipNested)
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{
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if (*it==NULL)
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{
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val->type=jbvNull;
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returnWJB_DONE;
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}
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/*
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* When stepping into a nested container, we jump back here to start
@@ -898,6 +900,7 @@ JsonbIteratorNext(JsonbIterator **it, JsonbValue *val, bool skipNested)
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* nesting).
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*/
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*it=freeAndGetParent(*it);
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val->type=jbvNull;
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returnWJB_END_ARRAY;
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}
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@@ -951,6 +954,7 @@ JsonbIteratorNext(JsonbIterator **it, JsonbValue *val, bool skipNested)
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* of nesting).
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*/
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*it=freeAndGetParent(*it);
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val->type=jbvNull;
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returnWJB_END_OBJECT;
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}
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else
@@ -995,8 +999,10 @@ JsonbIteratorNext(JsonbIterator **it, JsonbValue *val, bool skipNested)
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returnWJB_VALUE;
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}
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elog(ERROR,"invalid iterator state");
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return-1;
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elog(ERROR,"invalid jsonb iterator state");
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/* satisfy compilers that don't know that elog(ERROR) doesn't return */
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val->type=jbvNull;
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returnWJB_DONE;
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}
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/*

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