[flang-commits] [flang] 89e4d9f - [Flang] Fix crash with parametrized derived types usage (#150289)

[via flang-commits]

Author: Carlos Seo
Date: 2025-08-01T11:20:09-03:00
New Revision: 89e4d9f905f7abbf5803c011ab6fba26796ced30

URL: https://github.com/llvm/llvm-project/commit/89e4d9f905f7abbf5803c011ab6fba26796ced30
DIFF: https://github.com/llvm/llvm-project/commit/89e4d9f905f7abbf5803c011ab6fba26796ced30.diff

LOG: [Flang] Fix crash with parametrized derived types usage (#150289)

The current mangleName implementation doesn't take a FoldingContext,
which prevents the proper evaluation of expressions containing parameter
references to an integer constant. Since parametrized derived types are
not yet implemented, the compiler will crash there in some cases (see
example in issue #127424).

This is a workaround so that doesn't happen until the feature is
properly implemented.

Fixes #127424

Added: 
    flang/test/Lower/parametrized-derived-types.f90

Modified: 
    flang/lib/Lower/Mangler.cpp

Removed: 
    


################################################################################
diff  --git a/flang/lib/Lower/Mangler.cpp b/flang/lib/Lower/Mangler.cpp
index 1333e3fe349d1..e1ae86a1b5bb2 100644
--- a/flang/lib/Lower/Mangler.cpp
+++ b/flang/lib/Lower/Mangler.cpp
@@ -224,8 +224,18 @@ std::string Fortran::lower::mangle::mangleName(
       assert(paramExpr && "derived type kind param not explicit");
       std::optional<int64_t> init =
           Fortran::evaluate::ToInt64(paramValue->GetExplicit());
-      assert(init && "derived type kind param is not constant");
-      kinds.emplace_back(*init);
+      // TODO: put the assertion check back when parametrized derived types
+      // are supported:
+      // assert(init && "derived type kind param is not constant");
+      //
+      // The init parameter above will require a FoldingContext for proper
+      // expression evaluation to an integer constant, otherwise the
+      // compiler may crash here (see example in issue #127424).
+      if (!init) {
+        TODO_NOLOC("parameterized derived types");
+      } else {
+        kinds.emplace_back(*init);
+      }
     }
   }
   return fir::NameUniquer::doType(modules, procs, blockId, symbolName, kinds);

diff  --git a/flang/test/Lower/parametrized-derived-types.f90 b/flang/test/Lower/parametrized-derived-types.f90
new file mode 100644
index 0000000000000..97a40c9169d2b
--- /dev/null
+++ b/flang/test/Lower/parametrized-derived-types.f90
@@ -0,0 +1,19 @@
+! RUN: %python %S/test_errors.py %s %flang_fc1
+! XFAIL: *
+program main
+  TYPE ty(k1,k2)
+     INTEGER ,KIND::k1,k2=5
+     INTEGER::arr(k1:k2)=10
+     CHARACTER(LEN=k2)::CHARACTER
+  END TYPE ty
+  TYPE,EXTENDS(ty)::ty1(k3)
+     INTEGER,KIND ::k3=4
+     TYPE(ty(2,k3+1))::cmp_ty = ty(2,k3+1)(55,'HI')
+  END TYPE ty1
+  TYPE ty2(l1, l2)
+  !ERROR: not yet implemented: parameterized derived types
+     INTEGER,LEN ::l1,l2
+     TYPE(ty1(2,5)), ALLOCATABLE::ty1_cmp(:)
+  END TYPE ty2
+  TYPE(ty2(4,8)) ::ty2_obj
+end program main