Fix instantiation of array state variables

src/codegen/codegen_cpp_visitor.cpp

@@ -3330,7 +3330,13 @@ void CodegenCppVisitor::print_initial_block(const InitialBlock* node) {
         if (!info.is_ionic_conc(name)) {
             auto lhs = get_variable_name(name);
             auto rhs = get_variable_name(name + "0");
-            printer->fmt_line("{} = {};", lhs, rhs);
+            if (var->is_array()) {
+                for (int i = 0; i < var->get_length(); ++i) {
+                    printer->fmt_line("{}[{}] = {};", lhs, i, rhs);
+                }
+            } else {
+                printer->fmt_line("{} = {};", lhs, rhs);
+            }
         }
     }
 

test/unit/codegen/codegen_cpp_visitor.cpp

@@ -1181,3 +1181,57 @@ SCENARIO("Check codegen for MUTEX and PROTECT", "[codegen][mutex_protect]") {
         }
     }
 }
+
+
+SCENARIO("Array STATE variable", "[codegen][array_state]") {
+    GIVEN("A mod file containing an array STATE variable") {
+        std::string const nmodl_text = R"(
+            DEFINE NANN  4
+
+            NEURON {
+                SUFFIX ca_test
+            }
+            STATE {
+                ca[NANN]
+                k
+            }
+        )";
+
+        THEN("nrn_init is printed with proper initialization of the whole array") {
+            auto const generated = get_cpp_code(nmodl_text);
+            std::string expected_code_init =
+                R"(/** initialize channel */
+    void nrn_init_ca_test(NrnThread* nt, Memb_list* ml, int type) {
+        int nodecount = ml->nodecount;
+        int pnodecount = ml->_nodecount_padded;
+        const int* node_index = ml->nodeindices;
+        double* data = ml->data;
+        const double* voltage = nt->_actual_v;
+        Datum* indexes = ml->pdata;
+        ThreadDatum* thread = ml->_thread;
+
+        setup_instance(nt, ml);
+        auto* const inst = static_cast<ca_test_Instance*>(ml->instance);
+
+        if (_nrn_skip_initmodel == 0) {
+            #pragma omp simd
+            #pragma ivdep
+            for (int id = 0; id < nodecount; id++) {
+                int node_id = node_index[id];
+                double v = voltage[node_id];
+                #if NRN_PRCELLSTATE
+                inst->v_unused[id] = v;
+                #endif
+                (inst->ca+id*4)[0] = inst->global->ca0;
+                (inst->ca+id*4)[1] = inst->global->ca0;
+                (inst->ca+id*4)[2] = inst->global->ca0;
+                (inst->ca+id*4)[3] = inst->global->ca0;
+                inst->k[id] = inst->global->k0;
+            }
+        }
+    })";
+
+            REQUIRE_THAT(generated, ContainsSubstring(expected_code_init));
+        }
+    }
+}