[issue7238] frame.f_lineno doesn't get updated after local trace function assigned to it
report at bugs.python.org
Wed Nov 24 15:08:12 CET 2010
Ray.Allen <ysj.ray at gmail.com> added the comment:
It's not a bug. What happens is like this:
1, You set trace function using sys.settrace(tracer).
2, When the following func() is called, tracer is called with a "call" event, so the trace function in PyThreadState is set to NULL since "sys.settrace(None)" is execute, but since the return value is a valid local trace function, the frame of called function("func()") has its local trace function.
3, The called function("func()") executes, though its frame has a local trace function, but it will not be executed since PyThreadState->c_tracefunc is NULL. When you get f_lineno from frame, you get the not refreshed f_lineno value but not the dynamically computed lineno, as the f_lineno's getter function said:
return PyCode_Addr2Line(f->f_code, f->f_lasti);
Here because your frame's local trace function is not executed, the f_lineno is not refreshed.
4, When the second time func() calls, there is no global trace function. Each time you get the f_lineno, it uses PyCode_Addr2Line() to get the dynamically computed line number.
I think this situation is so rarely that the doc saying "f_lineno is
the current line number of the frame" is correct.
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