Clean up assorted failures under clang's -fsanitize=undefined checks.

Most of these are cases where we could call memcpy() or other libc
functions with a NULL pointer and a zero count, which is forbidden
by POSIX even though every production version of libc allows it.
We've fixed such things before in a piecemeal way, but apparently
never made an effort to try to get them all.  I don't claim that
this patch does so either, but it gets every failure I observe in
check-world, using clang 12.0.1 on current RHEL8.

numeric.c has a different issue that the sanitizer doesn't like:
"ln(-1.0)" will compute log10(0) and then try to assign the
resulting -Inf to an integer variable.  We don't actually use the
result in such a case, so there's no live bug.

Back-patch to all supported branches, with the idea that we might
start running a buildfarm member that tests this case.  This includes
back-patching c1132aae3 (Check the size in COPY_POINTER_FIELD),
which previously silenced some of these issues in copyfuncs.c.

Discussion: https://postgr.es/m/CALNJ-vT9r0DSsAOw9OXVJFxLENoVS_68kJ5x0p44atoYH+H4dg@mail.gmail.com

1 files changed, 21 insertions, 33 deletions

diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 5a98e9714d5..3703845b010 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -57,8 +57,11 @@
 #define COPY_POINTER_FIELD(fldname, sz) \
 	do { \
 		Size	_size = (sz); \
-		newnode->fldname = palloc(_size); \
-		memcpy(newnode->fldname, from->fldname, _size); \
+		if (_size > 0) \
+		{ \
+			newnode->fldname = palloc(_size); \
+			memcpy(newnode->fldname, from->fldname, _size); \
+		} \
 	} while (0)
 
 /* Copy a parse location field (for Copy, this is same as scalar case) */
@@ -293,12 +296,9 @@ _copyRecursiveUnion(const RecursiveUnion *from)
 	 */
 	COPY_SCALAR_FIELD(wtParam);
 	COPY_SCALAR_FIELD(numCols);
-	if (from->numCols > 0)
-	{
-		COPY_POINTER_FIELD(dupColIdx, from->numCols * sizeof(AttrNumber));
-		COPY_POINTER_FIELD(dupOperators, from->numCols * sizeof(Oid));
-		COPY_POINTER_FIELD(dupCollations, from->numCols * sizeof(Oid));
-	}
+	COPY_POINTER_FIELD(dupColIdx, from->numCols * sizeof(AttrNumber));
+	COPY_POINTER_FIELD(dupOperators, from->numCols * sizeof(Oid));
+	COPY_POINTER_FIELD(dupCollations, from->numCols * sizeof(Oid));
 	COPY_SCALAR_FIELD(numGroups);
 
 	return newnode;
@@ -872,13 +872,10 @@ _copyMergeJoin(const MergeJoin *from)
 	COPY_SCALAR_FIELD(skip_mark_restore);
 	COPY_NODE_FIELD(mergeclauses);
 	numCols = list_length(from->mergeclauses);
-	if (numCols > 0)
-	{
-		COPY_POINTER_FIELD(mergeFamilies, numCols * sizeof(Oid));
-		COPY_POINTER_FIELD(mergeCollations, numCols * sizeof(Oid));
-		COPY_POINTER_FIELD(mergeStrategies, numCols * sizeof(int));
-		COPY_POINTER_FIELD(mergeNullsFirst, numCols * sizeof(bool));
-	}
+	COPY_POINTER_FIELD(mergeFamilies, numCols * sizeof(Oid));
+	COPY_POINTER_FIELD(mergeCollations, numCols * sizeof(Oid));
+	COPY_POINTER_FIELD(mergeStrategies, numCols * sizeof(int));
+	COPY_POINTER_FIELD(mergeNullsFirst, numCols * sizeof(bool));
 
 	return newnode;
 }
@@ -979,12 +976,9 @@ _copyAgg(const Agg *from)
 	COPY_SCALAR_FIELD(aggstrategy);
 	COPY_SCALAR_FIELD(aggsplit);
 	COPY_SCALAR_FIELD(numCols);
-	if (from->numCols > 0)
-	{
-		COPY_POINTER_FIELD(grpColIdx, from->numCols * sizeof(AttrNumber));
-		COPY_POINTER_FIELD(grpOperators, from->numCols * sizeof(Oid));
-		COPY_POINTER_FIELD(grpCollations, from->numCols * sizeof(Oid));
-	}
+	COPY_POINTER_FIELD(grpColIdx, from->numCols * sizeof(AttrNumber));
+	COPY_POINTER_FIELD(grpOperators, from->numCols * sizeof(Oid));
+	COPY_POINTER_FIELD(grpCollations, from->numCols * sizeof(Oid));
 	COPY_SCALAR_FIELD(numGroups);
 	COPY_BITMAPSET_FIELD(aggParams);
 	COPY_NODE_FIELD(groupingSets);
@@ -1005,19 +999,13 @@ _copyWindowAgg(const WindowAgg *from)
 
 	COPY_SCALAR_FIELD(winref);
 	COPY_SCALAR_FIELD(partNumCols);
-	if (from->partNumCols > 0)
-	{
-		COPY_POINTER_FIELD(partColIdx, from->partNumCols * sizeof(AttrNumber));
-		COPY_POINTER_FIELD(partOperators, from->partNumCols * sizeof(Oid));
-		COPY_POINTER_FIELD(partCollations, from->partNumCols * sizeof(Oid));
-	}
+	COPY_POINTER_FIELD(partColIdx, from->partNumCols * sizeof(AttrNumber));
+	COPY_POINTER_FIELD(partOperators, from->partNumCols * sizeof(Oid));
+	COPY_POINTER_FIELD(partCollations, from->partNumCols * sizeof(Oid));
 	COPY_SCALAR_FIELD(ordNumCols);
-	if (from->ordNumCols > 0)
-	{
-		COPY_POINTER_FIELD(ordColIdx, from->ordNumCols * sizeof(AttrNumber));
-		COPY_POINTER_FIELD(ordOperators, from->ordNumCols * sizeof(Oid));
-		COPY_POINTER_FIELD(ordCollations, from->ordNumCols * sizeof(Oid));
-	}
+	COPY_POINTER_FIELD(ordColIdx, from->ordNumCols * sizeof(AttrNumber));
+	COPY_POINTER_FIELD(ordOperators, from->ordNumCols * sizeof(Oid));
+	COPY_POINTER_FIELD(ordCollations, from->ordNumCols * sizeof(Oid));
 	COPY_SCALAR_FIELD(frameOptions);
 	COPY_NODE_FIELD(startOffset);
 	COPY_NODE_FIELD(endOffset);