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PEP 657: Update the env variable name and the C-API and add some clarifications #2015

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PEP 657: Update the env variable name and the C-API and add some clarifications #2015

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23 changes: 16 additions & 7 deletions pep-0657.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -191,11 +191,16 @@ this PEP:
four-element tuples containing the full location of every instruction
(including start line, end line, start column offset and end column offset)
or ``None`` if the code object was created without the offset information.
* Three new C-API functions, ``PyCode_Addr2EndLine``, ``PyCode_Addr2StartOffset``
and ``PyCode_Addr2EndOffset`` will be added that can obtain the end line, the
start column offsets and the end column offset respectively given the index
of a bytecode instruction. These functions will return 0 if the information
is not available.
* One new C-API function: ::

int PyCode_Addr2Location(
PyCodeObject *co, int addr,
int *startline, int *startcolumn,
int *endline, int *endcolumn)

will be added so the end line, the start column offsets and the end column
offset can be obtained given the index of a bytecode instruction. This
function will set the values to 0 if the information is not available.
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The internal storage, compression and encoding of the information is left as an
implementation detail and can be changed at any point as long as the public API
Expand Down Expand Up @@ -311,18 +316,22 @@ storage and memory overhead and to allow third party tools and other
programs that are currently parsing tracebacks to catch up the following
methods will be provided to deactivate this feature:

* A new environment variable: ``PYNODEBUGRANGES``.
* A new environment variable: ``PYTHONNODEBUGRANGES``.
* A new command line option for the dev mode: ``python -Xnodebugranges``.

If any of these methods are used, the Python compiler will **not** populate
code objects with the new information (``None`` will be used instead) and any
unmarshalled code objects that contain the extra information will have it stripped
away and replaced with ``None``). This method allows users to:
away and replaced with ``None``). Additionally, the traceback machinery will not
show the extended location information even if the information was present.
This method allows users to:

* Create smaller ``pyc`` files by using one of the two methods when said files
are created.
* Don't load the extra information from ``pyc`` files if those were created with
the extra information in the first place.
* Deactivate the extra information when displaying tracebacks (the caret characters
indicating the location of the error).

Doing this has a **very small** performance hit as the interpreter state needs
to be fetched when code objects are created to look up the configuration.
Expand Down