Statistics

# All branches
$ git log --after=2017-03-31 --before=2017-06-30 --reverse --branches='*' --author=Stinner > 2017Q2
$ grep '^commit ' 2017Q2|wc -l
222

# Master branch only
$ git log --after=2017-03-31 --before=2017-06-30 --reverse --author=Stinner origin/master|grep '^commit '|wc -l
85

Statistics: 85 commits in the master branch, a total of 222 commits: most (but not all) of the remaining 137 commits are cherry-picked backports to 2.7, 3.5 and 3.6 branches.

Note: I didn't use --no-merges since we don't use merge anymore, but git cherry-pick -x, to backport fixes. Before GitHub, we used forwardport with Mercurial merges (ex: commit into 3.6, then merge into master).

Buildbots and test.bisect

Since this article became way too long, I splitted it into sub-articles:

• New Python test.bisect tool
• Work on Python buildbots, 2017 Q2

Python 3.6.0 regression

I am ashamed, I introduced a tricky regression in Pyton 3.6.0 with my work on FASTCALL optimizations :-( A special way to call C builtin functions was broken:

from datetime import datetime
next(iter(datetime.now, None))

This code raises a StopIteration exception instead of formatting the current date and time.

It's even worse. I was aware of the bug, it was already fixed it in master, but I just forgot to backport my fix: bpo-30524, fix _PyStack_UnpackDict().

To prevent regressions, I wrote exhaustive unit tests on the 3 FASTCALL functions, commit: bpo-30524: Write unit tests for FASTCALL

struct.Struct.format type

Sometimes, fixing a bug can take longer than expected. In March 2014, Zbyszek Jędrzejewski-Szmek reported a bug on the format attribute of the struct.Struct class: this attribute type is bytes, whereas a Unicode string (str) was expected.

I proposed to "just" change the attribute type in December 2014, but it was an incompatible change which would break the backward compatibility. Martin Panter agreed and wrote a patch. Serhiy Storchaka asked to discuss such incompatible change on python-dev, but then nothing happened during longer than... 2 years!

In March 2017, I converted the old Martin's patch into a new GitHub pull request. Serhiy asked again to write to python-dev, so I wrote: Issue #21071: change struct.Struct.format type from bytes to str. And... I got zero answer.

Well, I didn't expect any, since it's a trivial change, and I don't expect that anyone rely on the exact format attribute type. Moreover, the struct.Struct constructor already accepts bytes and str types. If the attribute is passed to the constructor: it just works.

In June 2017, Serhiy Storchaka replied to my email: If nobody opposed to this change it will be made in short time.

Since nobody replied, again, I just merged my pull request. So it took 3 years and 3 months to change the type of an uncommon attribute :-)

Note: I never used this attribute... Before reading this issue, I didn't even know that the struct module has a struct.Struct type...

Optimization: one less syscall per open() call

In bpo-30228, I modified FileIO.seek() and FileIO.tell() methods to now set the internal seekable attribute to avoid one fstat() syscall per Python open() call in buffered or text mode.

The seekable property is now also more reliable since its value is set correctly on memory allocation failure.

I still have a second pending pull request to remove one more fstat() syscall: bpo-30228: TextIOWrapper uses abs_pos, not tell().

make regen-all

I started to look at bpo-23404, because the Python compilation failed on the "AMD64 FreeBSD 9.x 3.x" buildbot when trying to regenerate the Include/opcode.h file.