Further SET_LINENO reomval fixes. See comments in patch #587933.

Use a slightly different strategy to determine when not to call the line
trace function.  This removes the need for the RETURN_NONE opcode, so
that's gone again.  Update docs and comments to match.

Thanks to Neal and Armin!

Also add a test suite.  This should have come with the original patch...

2 files changed, 2 insertions, 14 deletions

diff --git a/Doc/lib/libdis.tex b/Doc/lib/libdis.tex
index 567c0ee..7bdd239 100644
--- a/Doc/lib/libdis.tex
+++ b/Doc/lib/libdis.tex
@@ -27,7 +27,8 @@ the following command can be used to get the disassembly of
               3 LOAD_FAST                0 (alist)
               6 CALL_FUNCTION            1
               9 RETURN_VALUE        
-             10 RETURN_NONE
+             10 LOAD_CONST               0 (None)
+             13 RETURN_VALUE
 \end{verbatim}
 
 (The ``2'' is a line number).
@@ -401,14 +402,6 @@ is evaluated, the locals are passed to the class definition.
 Returns with TOS to the caller of the function.
 \end{opcodedesc}
 
-\begin{opcodedesc}{RETURN_NONE}{}
-Returns \constant{None} to the caller of the function.  This opcode is
-generated as the last opcode of every function and only then, for
-reasons to do with tracing support.  See the comments in the function
-\cfunction{maybe_call_line_trace} in \file{Python/ceval.c} for the
-gory details.  \versionadded{2.3}.
-\end{opcodedesc}
-
 \begin{opcodedesc}{YIELD_VALUE}{}
 Pops \code{TOS} and yields it from a generator.
 \end{opcodedesc}
diff --git a/Doc/whatsnew/whatsnew23.tex b/Doc/whatsnew/whatsnew23.tex
index a971791..ff16de1 100644
--- a/Doc/whatsnew/whatsnew23.tex
+++ b/Doc/whatsnew/whatsnew23.tex
@@ -1225,11 +1225,6 @@ should instead call \code{PyCode_Addr2Line(f->f_code, f->f_lasti)}.
 This will have the added effect of making the code work as desired
 under ``python -O'' in earlier versions of Python.
 
-To make tracing work as expected, it was found necessary to add a new
-opcode, \cdata{RETURN_NONE}, to the VM.  If you want to know why, read
-the comments in the function \cfunction{maybe_call_line_trace} in
-\file{Python/ceval.c}.
-
 \end{itemize}