[flang-commits] [flang] ebec4d6 - [flang] Fix use-after-free cases found by valgrind (#122394)

[via flang-commits]

Author: Peter Klausler
Date: 2025-01-14T12:56:33-08:00
New Revision: ebec4d6369cbf9bbd64236b02d90e8f3597ad103

URL: https://github.com/llvm/llvm-project/commit/ebec4d6369cbf9bbd64236b02d90e8f3597ad103
DIFF: https://github.com/llvm/llvm-project/commit/ebec4d6369cbf9bbd64236b02d90e8f3597ad103.diff

LOG: [flang] Fix use-after-free cases found by valgrind (#122394)

The expression traversal library needs to use interfaces into triplets
(and substrings) that return pointers to nested expressions, rather than
optional copies of them, since at least one semantic analysis collects a
set of references to some subexpression representation class instances,
and those references obviously can't point to local copies of objects.

Fixes https://github.com/llvm/llvm-project/issues/121999.

Added: 
    

Modified: 
    flang/include/flang/Evaluate/traverse.h
    flang/include/flang/Evaluate/variable.h

Removed: 
    


################################################################################
diff  --git a/flang/include/flang/Evaluate/traverse.h b/flang/include/flang/Evaluate/traverse.h
index 90b93f6afd3515..dd38d64bff63f7 100644
--- a/flang/include/flang/Evaluate/traverse.h
+++ b/flang/include/flang/Evaluate/traverse.h
@@ -139,7 +139,7 @@ class Traverse {
     return visitor_(x.base());
   }
   Result operator()(const Triplet &x) const {
-    return Combine(x.lower(), x.upper(), x.stride());
+    return Combine(x.GetLower(), x.GetUpper(), x.GetStride());
   }
   Result operator()(const Subscript &x) const { return visitor_(x.u); }
   Result operator()(const ArrayRef &x) const {
@@ -151,7 +151,7 @@ class Traverse {
   }
   Result operator()(const DataRef &x) const { return visitor_(x.u); }
   Result operator()(const Substring &x) const {
-    return Combine(x.parent(), x.lower(), x.upper());
+    return Combine(x.parent(), x.GetLower(), x.GetUpper());
   }
   Result operator()(const ComplexPart &x) const {
     return visitor_(x.complex());

diff  --git a/flang/include/flang/Evaluate/variable.h b/flang/include/flang/Evaluate/variable.h
index b454d37d93e57b..9b597d29813da1 100644
--- a/flang/include/flang/Evaluate/variable.h
+++ b/flang/include/flang/Evaluate/variable.h
@@ -331,8 +331,14 @@ class Substring {
   }
 
   Expr<SubscriptInteger> lower() const;
+  const Expr<SubscriptInteger> *GetLower() const {
+    return lower_.has_value() ? &lower_->value() : nullptr;
+  }
   Substring &set_lower(Expr<SubscriptInteger> &&);
   std::optional<Expr<SubscriptInteger>> upper() const;
+  const Expr<SubscriptInteger> *GetUpper() const {
+    return upper_.has_value() ? &upper_->value() : nullptr;
+  }
   Substring &set_upper(Expr<SubscriptInteger> &&);
   const Parent &parent() const { return parent_; }
   Parent &parent() { return parent_; }