Properly reset 'DoNotUse' tag property on overwrite.

Author: MaxSagebaum

documentation/Changelog.md

@@ -5,6 +5,9 @@ Changelog {#Changelog}
  - Features:
    * Specialization for Eigen math traits.
 
+ - Bugfix:
+   * Tag property 'DoNotUse' is now properly reset on overwrite.
+
 ### v3.1.0 - 2026-02-02
  - Features:
    * It is now possible to define custom tape evaluators for all CoDiPack tapes. The evaluators have access to the full

include/codi/tapes/tagging/tagTapeBase.hpp

@@ -207,6 +207,7 @@ namespace codi {
           } else {
             resetTag(lhs.values[i.value].getTapeData().tag);
           }
+          lhs.values[i.value].getTapeData().properties.reset(TagFlags::DoNotUse);
           lhs.values[i.value].value() = AggregatedTraits::template arrayAccess<i.value>(real);
         });
       }
@@ -236,6 +237,7 @@ namespace codi {
         } else {
           resetTag(lhs.cast().getTapeData().tag);
         }
+        lhs.cast().getTapeData().properties.reset(TagFlags::DoNotUse);
 
         lhs.cast().value() = rhs.cast().getValue();
       }

tests/functional/src/testTagging.cpp

@@ -95,9 +95,12 @@ int main(int nargs, char** args) {
   w = w * z;
 
   out << "Do not use error:" << std::endl;
-  tape.setTagPropertyOnVariable(x, codi::TagFlags::DoNotUse);
-  w = func(x, y);
-  tape.clearTagPropertiesOnVariable(x);
+  Real t = x;
+  tape.setTagPropertyOnVariable(t, codi::TagFlags::DoNotUse);
+  w = func(t, y); // Error is thrown.
+  t = func(x, y); // t is overwritten
+  w = func(t, y); // Error is not thrown.
+  w = func(x, y); // Reset w.
 
   out << "Do not change with same value:" << std::endl;
   tape.setTagPropertyOnVariable(w, codi::TagFlags::DoNotChange);