bpo-31344: Per-frame control of trace events (GH-3417)

f_trace_lines: enable/disable line trace events
f_trace_opcodes: enable/disable opcode trace events

These are intended primarily for testing of the interpreter
itself, as they make it much easier to emulate signals
arriving at unfortunate times.

1 files changed, 12 insertions, 5 deletions

diff --git a/Python/ceval.c b/Python/ceval.c
index 8fc65cdcc0..a072a5fe81 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -4458,12 +4458,19 @@ maybe_call_line_trace(Py_tracefunc func, PyObject *obj,
         *instr_lb = bounds.ap_lower;
         *instr_ub = bounds.ap_upper;
     }
-    /* If the last instruction falls at the start of a line or if
-       it represents a jump backwards, update the frame's line
-       number and call the trace function. */
-    if (frame->f_lasti == *instr_lb || frame->f_lasti < *instr_prev) {
+    /* Always emit an opcode event if we're tracing all opcodes. */
+    if (frame->f_trace_opcodes) {
+        result = call_trace(func, obj, tstate, frame, PyTrace_OPCODE, Py_None);
+    }
+    /* If the last instruction falls at the start of a line or if it
+       represents a jump backwards, update the frame's line number and
+       then call the trace function if we're tracing source lines.
+    */
+    if ((frame->f_lasti == *instr_lb || frame->f_lasti < *instr_prev)) {
         frame->f_lineno = line;
-        result = call_trace(func, obj, tstate, frame, PyTrace_LINE, Py_None);
+        if (frame->f_trace_lines) {
+            result = call_trace(func, obj, tstate, frame, PyTrace_LINE, Py_None);
+        }
     }
     *instr_prev = frame->f_lasti;
     return result;