Fix sanitizer CI for IDA init/source-current hoctests

UBSan aborted LinearMechanism construction: NrnDAE bound references to
optional-null elayer and y0 Vectors. Defer those dereferences until the
pointers are known non-null.

macOS ASan/TSan aborted isolated python -c children because SIP drops
DYLD_INSERT_LIBRARIES. Re-apply NRN_SANITIZER_PRELOAD_* (same pattern as
test_basic.py) so interceptors load before dlopen of libnrniv.

Author: nrnhines

src/nrniv/nrndae.cpp

@@ -187,14 +187,13 @@ NrnDAE::NrnDAE(Matrix* cmat,
         cmat = assumed_identity_;
     }
     c_ = new MatrixMap(cmat);
-    Vect& elay = *elayer;
     nnode_ = nnode;
     nodes_ = nodes;
     if (nnode_ > 0) {
         elayer_ = new int[nnode_];
         if (elayer) {
             for (int i = 0; i < nnode_; ++i) {
-                elayer_[i] = int(elay[i]);
+                elayer_[i] = int((*elayer)[i]);
             }
         } else {
             for (int i = 0; i < nnode_; ++i) {
@@ -260,20 +259,17 @@ void NrnDAE::update() {
 void NrnDAE::init() {
     // printf("NrnDAE::init %lx\n", (long)this);
     // printf("init size_=%d %d %d %d\n", size_, y_->size(), y0_->size(), b_->size());
-    Vect& y0 = *y0_;
 
     v2y();
     if (f_init_) {
         f_init_(data_);
+    } else if (y0_) {
+        for (int i = nnode_; i < size_; ++i) {
+            y_[i] = (*y0_)[i];
+        }
     } else {
-        if (y0_) {
-            for (int i = nnode_; i < size_; ++i) {
-                y_[i] = y0[i];
-            }
-        } else {
-            for (int i = nnode_; i < size_; ++i) {
-                y_[i] = 0.;
-            }
+        for (int i = nnode_; i < size_; ++i) {
+            y_[i] = 0.;
         }
     }
     // for (i=0; i < nnode_; ++i) printf(" i=%d y[i]=%g\n", i, y[i]);

test/hoctests/tests/test_ida_init_mode.py

@@ -72,10 +72,23 @@ def test_dae_init_stats_api():
     assert "ok" in _run_isolated(code)
 
 
+def _sanitizer_child_env(env=None):
+    """Re-apply sanitizer preload for macOS SIP (see NeuronTestHelper.cmake)."""
+    env = os.environ.copy() if env is None else env
+    try:
+        env[os.environ["NRN_SANITIZER_PRELOAD_VAR"]] = os.environ[
+            "NRN_SANITIZER_PRELOAD_VAL"
+        ]
+    except KeyError:
+        pass
+    return env
+
+
 def _run_isolated(code: str):
-    env = os.environ.copy()
+    env = _sanitizer_child_env()
+    exe = os.environ.get("NRN_PYTHON_EXECUTABLE", sys.executable)
     r = subprocess.run(
-        [sys.executable, "-c", code],
+        [exe, "-c", code],
         env=env,
         capture_output=True,
         text=True,

test/hoctests/tests/test_ida_source_current.py

@@ -98,18 +98,31 @@ def _build_pwlclamp_mech_dir() -> str:
     return arch
 
 
+def _sanitizer_child_env(env=None):
+    """Re-apply sanitizer preload for macOS SIP (see NeuronTestHelper.cmake)."""
+    env = os.environ.copy() if env is None else env
+    try:
+        env[os.environ["NRN_SANITIZER_PRELOAD_VAR"]] = os.environ[
+            "NRN_SANITIZER_PRELOAD_VAL"
+        ]
+    except KeyError:
+        pass
+    return env
+
+
 def _run_isolated(code: str, timeout: float = 120.0) -> str:
     """Run code in a subprocess with the same interpreter/env; return stdout."""
-    env = os.environ.copy()
+    env = _sanitizer_child_env()
     # Point children at a ready PWLClamp mechanism directory
     try:
         env["NRN_PWLCLAMP_MECH"] = _build_pwlclamp_mech_dir()
     except Exception as e:
         # IClamp-only tests do not need the mech
         env.pop("NRN_PWLCLAMP_MECH", None)
         env["NRN_PWLCLAMP_BUILD_ERR"] = str(e)
+    exe = os.environ.get("NRN_PYTHON_EXECUTABLE", sys.executable)
     proc = subprocess.run(
-        [sys.executable, "-c", code],
+        [exe, "-c", code],
         capture_output=True,
         text=True,
         timeout=timeout,