[flang] Fix crash on erroneous program (#88192)

klausler · web-flow · commit 138524ef8ea9 · 2024-04-22T15:01:01.000-07:00
Constant folding had a CHECK on array subscript rank that should more gracefully handle a bad program with a subscript that is a matrix or higher rank. Fixes #88112.
diff --git a/flang/lib/Evaluate/fold-implementation.h b/flang/lib/Evaluate/fold-implementation.h
@@ -201,11 +201,12 @@ std::optional<Constant<T>> Folder<T>::ApplySubscripts(const Constant<T> &array,
   ConstantSubscripts resultShape;
   ConstantSubscripts ssLB;
   for (const auto &ss : subscripts) {
-    CHECK(ss.Rank() <= 1);
     if (ss.Rank() == 1) {
       resultShape.push_back(static_cast<ConstantSubscript>(ss.size()));
       elements *= ss.size();
       ssLB.push_back(ss.lbounds().front());
+    } else if (ss.Rank() > 1) {
+      return std::nullopt; // error recovery
     }
   }
   ConstantSubscripts ssAt(rank, 0), at(rank, 0), tmp(1, 0);

Original file line number	Diff line number	Diff line change
`@@ -201,11 +201,12 @@ std::optional<Constant<T>> Folder<T>::ApplySubscripts(const Constant<T> &array,`
`201`	`201`	`ConstantSubscripts resultShape;`
`202`	`202`	`ConstantSubscripts ssLB;`
`203`	`203`	`for (const auto &ss : subscripts) {`
`204`		`- CHECK(ss.Rank() <= 1);`
`205`	`204`	`if (ss.Rank() == 1) {`
`206`	`205`	`resultShape.push_back(static_cast<ConstantSubscript>(ss.size()));`
`207`	`206`	`elements *= ss.size();`
`208`	`207`	`ssLB.push_back(ss.lbounds().front());`
	`208`	`+ } else if (ss.Rank() > 1) {`
	`209`	`+ return std::nullopt; // error recovery`
`209`	`210`	`}`
`210`	`211`	`}`
`211`	`212`	`ConstantSubscripts ssAt(rank, 0), at(rank, 0), tmp(1, 0);`