Replace HocTopContext* macros with class (#3279)

src/nrnpython/hoccontext.h

@@ -5,18 +5,6 @@ extern Objectdata* hoc_top_level_data;
 extern Symlist* hoc_top_level_symlist;
 extern Symlist* hoc_symlist;
 
-#define HocTopContextSet                       \
-    HocContext hcref;                          \
-    HocContext* hc_ = 0;                       \
-    if (hoc_thisobject) {                      \
-        hc_ = hc_save_and_set_to_top_(&hcref); \
-    }
-
-#define HocContextRestore \
-    if (hc_) {            \
-        hc_restore_(hc_); \
-    }
-
 struct HocContext {
     Object* obj;
     Objectdata* obd;
@@ -37,3 +25,23 @@ static void hc_restore_(HocContext* hc) {
     hoc_objectdata = hc->obd;
     hoc_symlist = hc->sl;
 }
+
+// RAII guard for the top HOC context
+class HocTopContextManager {
+  private:
+    HocContext hcref;
+    HocContext* hc_ = nullptr;
+
+  public:
+    HocTopContextManager() {
+        // ``hoc_thisobject`` is global
+        if (hoc_thisobject) {
+            hc_ = hc_save_and_set_to_top_(&hcref);
+        }
+    }
+    ~HocTopContextManager() {
+        if (hc_) {
+            hc_restore_(hc_);
+        }
+    }
+};

src/nrnpython/nrnpy_hoc.cpp

@@ -756,7 +756,7 @@ static void* fcall(void* vself, void* vargs) {
 
         return result;
     } else {
-        HocTopContextSet
+        auto interp = HocTopContextManager();
         Inst fc[4];
         // ugh. so a potential call of hoc_get_last_pointer_symbol will return nullptr.
         fc[0].in = STOP;
@@ -766,7 +766,6 @@ static void* fcall(void* vself, void* vargs) {
         Inst* pcsav = save_pc(fc + 1);
         hoc_call();
         hoc_pc = pcsav;
-        HocContextRestore;
     }
 
     return nrnpy_hoc_pop("laststatement fcall");
@@ -1263,7 +1262,7 @@ static PyObject* hocobj_getattr(PyObject* subself, PyObject* pyname) {
         }
     }
     // top level interpreter fork
-    HocTopContextSet
+    auto interp = HocTopContextManager();
     switch (sym->type) {
     case VAR:  // double*
         if (!is_array(*sym)) {
@@ -1373,7 +1372,6 @@ static PyObject* hocobj_getattr(PyObject* subself, PyObject* pyname) {
         }
     }
     }
-    HocContextRestore
     return result.release().ptr();
 }
 
@@ -1499,7 +1497,7 @@ static int hocobj_setattro(PyObject* subself, PyObject* pyname, PyObject* value)
             return -1;
         }
     }
-    HocTopContextSet
+    auto interp = HocTopContextManager();
     switch (sym->type) {
     case VAR:  // double*
         if (is_array(*sym)) {
@@ -1533,7 +1531,6 @@ static int hocobj_setattro(PyObject* subself, PyObject* pyname, PyObject* value)
             } else {
                 hoc_pushs(sym);
                 if (hoc_evalpointer_err()) {  // not possible to raise error.
-                    HocContextRestore;
                     return -1;
                 }
                 err = PyArg_Parse(value, "d", hoc_pxpop()) == 0;
@@ -1590,7 +1587,6 @@ static int hocobj_setattro(PyObject* subself, PyObject* pyname, PyObject* value)
         err = -1;
         break;
     }
-    HocContextRestore
     return err;
 }
 
@@ -2009,14 +2005,13 @@ static PyObject* hocobj_getitem(PyObject* self, Py_ssize_t ix) {
                 }
             }
         } else {  // must be a top level intermediate
-            HocTopContextSet
+            auto interp = HocTopContextManager();
             switch (po->sym_->type) {
             case VAR:
                 hocobj_pushtop(po, po->sym_, ix);
                 if (hoc_evalpointer_err()) {
                     --po->nindex_;
-                    HocContextRestore;
-                    return NULL;
+                    return nullptr;
                 }
                 --po->nindex_;
                 if (po->type_ == PyHoc::HocArrayIncomplete) {
@@ -2040,7 +2035,6 @@ static PyObject* hocobj_getitem(PyObject* self, Py_ssize_t ix) {
                 --po->nindex_;
                 break;
             }
-            HocContextRestore;
         }
     }
     return result.release().ptr();
@@ -2158,12 +2152,11 @@ static int hocobj_setitem(PyObject* self, Py_ssize_t i, PyObject* arg) {
             err = set_final_from_stk(arg);
         }
     } else {  // must be a top level intermediate
-        HocTopContextSet
+        auto interp = HocTopContextManager();
         switch (po->sym_->type) {
         case VAR:
             hocobj_pushtop(po, po->sym_, i);
             if (hoc_evalpointer_err()) {
-                HocContextRestore;
                 --po->nindex_;
                 return -1;
             }
@@ -2194,7 +2187,6 @@ static int hocobj_setitem(PyObject* self, Py_ssize_t i, PyObject* arg) {
             PyErr_SetString(PyExc_TypeError, "not assignable");
             break;
         }
-        HocContextRestore;
     }
     return err;
 }

src/nrnpython/nrnpy_p2h.cpp

@@ -100,7 +100,7 @@ static nb::object nrnpy_pyCallObject(nb::callable callable, nb::object args) {
     // When hoc calls a PythonObject method, then in case python
     // calls something back in hoc, the hoc interpreter must be
     // at the top level
-    HocTopContextSet
+    auto interp = HocTopContextManager();
     nb::tuple tup(args);
     nb::object p = nb::steal(PyObject_CallObject(callable.ptr(), tup.ptr()));
 #if 0
@@ -110,7 +110,6 @@ printf("\nargs\n");
 PyObject_Print(args, stdout, 0);
 printf("\nreturn %p\n", p);
 #endif
-    HocContextRestore
     // It would be nice to handle the error here, ending with a hoc_execerror
     // for any Exception (note, that does not include SystemExit). However
     // since many, but not all, of the callers need to clean up and

src/nrnpython/nrnpython.cpp

@@ -383,12 +383,11 @@ static int nrnpython_start(int b) {
 static void nrnpython_real() {
     int retval = 0;
 #if USE_PYTHON
-    HocTopContextSet
     {
+        auto interp = HocTopContextManager();
         nanobind::gil_scoped_acquire lock{};
         retval = (PyRun_SimpleString(hoc_gargstr(1)) == 0);
     }
-    HocContextRestore
 #endif
     hoc_retpushx(retval);
 }