coveragepy
diff --git a/‎coverage/core.py‎
Lines changed: 20 additions & 3 deletions b/‎coverage/core.py‎
Lines changed: 20 additions & 3 deletions
diff --git a/‎coverage/ctracer/module.c‎
Lines changed: 21 additions & 0 deletions b/‎coverage/ctracer/module.c‎
Lines changed: 21 additions & 0 deletions
@@ -70,6 +70,7 @@ def _debug(msg: str) -> None:
         _debug("in core.py")
 
         # Check the conditions that preclude us from using sys.monitoring.
+        # This applies to both sysmon and csysmon.
         reason_no_sysmon = ""
         if not env.PYBEHAVIOR.pep669:
             reason_no_sysmon = "sys.monitoring isn't available in this version"
@@ -89,9 +90,12 @@ def _debug(msg: str) -> None:
             core_name = config.core
             _debug(f"core.py: core from config is {core_name!r}")
 
-        if core_name == "sysmon" and reason_no_sysmon:
-            _debug(f"core.py: defaulting because sysmon not usable: {reason_no_sysmon}")
-            warn(f"Can't use core=sysmon: {reason_no_sysmon}, using default core", slug="no-sysmon")
+        if core_name in ("sysmon", "csysmon") and reason_no_sysmon:
+            _debug(f"core.py: defaulting because {core_name} not usable: {reason_no_sysmon}")
+            warn(
+                f"Can't use core={core_name}: {reason_no_sysmon}, using default core",
+                slug="no-sysmon",
+            )
             core_name = None
 
         if core_name is None:
@@ -108,6 +112,12 @@ def _debug(msg: str) -> None:
                     warn(f"Couldn't import C tracer: {IMPORT_ERROR}", slug="no-ctracer", once=True)
                 core_name = "pytrace"
                 _debug("core.py: Falling back to pytrace because C tracer not available")
+        elif core_name == "csysmon":
+            if not CTRACER_FILE:
+                if IMPORT_ERROR and env.SHIPPING_WHEELS:
+                    warn(f"Couldn't import C tracer: {IMPORT_ERROR}", slug="no-csysmon", once=True)
+                core_name = "sysmon"
+                _debug("core.py: Falling back to sysmon because C tracer not available")
 
         _debug(f"core.py: Using core={core_name}")
 
@@ -120,6 +130,13 @@ def _debug(msg: str) -> None:
             self.supports_plugins = False
             self.packed_arcs = False
             self.systrace = False
+        elif core_name == "csysmon":
+            self.tracer_class = coverage.tracer.CSysMonitor
+            self.tracer_kwargs["tool_id"] = 3 if metacov else 1
+            self.file_disposition_class = FileDisposition
+            self.supports_plugins = False
+            self.packed_arcs = False
+            self.systrace = False
         elif core_name == "ctrace":
             self.tracer_class = coverage.tracer.CTracer
             self.file_disposition_class = coverage.tracer.CFileDisposition
 
@@ -4,6 +4,7 @@
 #include "util.h"
 #include "tracer.h"
 #include "filedisp.h"
+#include "sysmon.h"
 
 /* Module definition */
 
@@ -22,6 +23,10 @@ tracer_exec(PyObject *mod)
         return -1;
     }
 
+    if (CSysMonitor_intern_strings() < 0) {
+        return -1;
+    }
+
     /* Initialize CTracer */
     CTracerType.tp_new = PyType_GenericNew;
     if (PyType_Ready(&CTracerType) < 0) {
@@ -48,6 +53,22 @@ tracer_exec(PyObject *mod)
         return -1;
     }
 
+    /* Initialize CSysMonitor */
+    CSysMonitorType.tp_new = PyType_GenericNew;
+    if (PyType_Ready(&CSysMonitorType) < 0) {
+        Py_DECREF(&CTracerType);
+        Py_DECREF(&CFileDispositionType);
+        return -1;
+    }
+
+    Py_INCREF(&CSysMonitorType);
+    if (PyModule_AddObject(mod, "CSysMonitor", (PyObject *)&CSysMonitorType) < 0) {
+        Py_DECREF(&CTracerType);
+        Py_DECREF(&CFileDispositionType);
+        Py_DECREF(&CSysMonitorType);
+        return -1;
+    }
+
     module_inited = TRUE;
     return 0;
 }