fix: adapt to a 3.13 change in frame.f_lasti

During a yield from a generator, frame.f_lasti used to point to the
YIELD bytecode.  In 3.13, it now points to the RESUME that follows it.
python/cpython#113728

Author: nedbat

coverage/ctracer/tracer.c

@@ -710,7 +710,10 @@ CTracer_handle_return(CTracer *self, PyFrameObject *frame)
                 real_return = TRUE;
             }
             else {
-                real_return = (code_bytes[lasti + 2] != RESUME);
+#if ENV_LASTI_IS_YIELD
+                lasti += 2;
+#endif
+                real_return = (code_bytes[lasti] != RESUME);
             }
 #else
             /* Need to distinguish between RETURN_VALUE and YIELD_VALUE. Read

coverage/ctracer/util.h

@@ -59,6 +59,11 @@
 #define MyCode_FreeCode(code)
 #endif
 
+// Where does frame.f_lasti point when yielding from a generator?
+// It used to point at the YIELD, now it points at the RESUME.
+// https://github.com/python/cpython/issues/113728
+#define ENV_LASTI_IS_YIELD (PY_VERSION_HEX < 0x030D0000)
+
 /* The values returned to indicate ok or error. */
 #define RET_OK      0
 #define RET_ERROR   -1

coverage/env.py

@@ -117,6 +117,11 @@ class PYBEHAVIOR:
     # PEP669 Low Impact Monitoring: https://peps.python.org/pep-0669/
     pep669 = bool(getattr(sys, "monitoring", None))
 
+    # Where does frame.f_lasti point when yielding from a generator?
+    # It used to point at the YIELD, now it points at the RESUME.
+    # https://github.com/python/cpython/issues/113728
+    lasti_is_yield = (PYVERSION < (3, 13))
+
 
 # Coverage.py specifics, about testing scenarios. See tests/testenv.py also.
 

coverage/pytracer.py

@@ -21,6 +21,7 @@
 )
 
 # We need the YIELD_VALUE opcode below, in a comparison-friendly form.
+# PYVERSIONS: RESUME is new in Python3.11
 RESUME = dis.opmap.get("RESUME")
 RETURN_VALUE = dis.opmap["RETURN_VALUE"]
 if RESUME is None:
@@ -137,7 +138,8 @@ def _trace(
         if THIS_FILE in frame.f_code.co_filename:
             return None
 
-        #self.log(":", frame.f_code.co_filename, frame.f_lineno, frame.f_code.co_name + "()", event)
+        # f = frame; code = f.f_code
+        # self.log(":", f"{code.co_filename} {f.f_lineno} {code.co_name}()", event)
 
         if (self.stopped and sys.gettrace() == self._cached_bound_method_trace):    # pylint: disable=comparison-with-callable
             # The PyTrace.stop() method has been called, possibly by another
@@ -255,8 +257,10 @@ def _trace(
                         # A return from the end of a code object is a real return.
                         real_return = True
                     else:
-                        # it's a real return.
-                        real_return = (code[lasti + 2] != RESUME)
+                        # It is a real return if we aren't going to resume next.
+                        if env.PYBEHAVIOR.lasti_is_yield:
+                            lasti += 2
+                        real_return = (code[lasti] != RESUME)
                 else:
                     if code[lasti] == RETURN_VALUE:
                         real_return = True