[flang][runtime] Accommodate change of type in assignment to allocatable (llvm#141988)

klausler · rorth · commit 62afaae7955e · 2025-06-11T14:12:25.000+02:00
When an assignment to a derived type allocatable requires (re)allocation, its type may change to that of the right-hand side. The code didn't update its derived type pointer, leading to the wrong type being put into the descriptors created for elemental defined assignment subroutine calls. Fixes llvm#141835.
diff --git a/flang-rt/lib/runtime/assign.cpp b/flang-rt/lib/runtime/assign.cpp
@@ -330,6 +330,7 @@ RT_API_ATTRS void Assign(Descriptor &to, const Descriptor &from,
       }
       flags &= ~NeedFinalization;
       toElementBytes = to.ElementBytes(); // may have changed
+      toDerived = toAddendum ? toAddendum->derivedType() : nullptr;
     }
   }
   if (toDerived && (flags & CanBeDefinedAssignment)) {

Original file line number	Diff line number	Diff line change
`@@ -330,6 +330,7 @@ RT_API_ATTRS void Assign(Descriptor &to, const Descriptor &from,`
`330`	`330`	`}`
`331`	`331`	`flags &= ~NeedFinalization;`
`332`	`332`	`toElementBytes = to.ElementBytes(); // may have changed`
	`333`	`+ toDerived = toAddendum ? toAddendum->derivedType() : nullptr;`
`333`	`334`	`}`
`334`	`335`	`}`
`335`	`336`	`if (toDerived && (flags & CanBeDefinedAssignment)) {`