[New-bugs-announce] [issue40145] Pyshellext room for binary size improvement

[Alexander Riccio]

New submission from Alexander Riccio <test35965 at gmail.com>:

I've tweaked the pcbuild options for pyshellext to reduce the size of the binary.
Since this is a very simple component, there really isn't much benefit of
optimizing for speed, likely the slowest part of this component's lifetime is
simply loading it.

This patch turns on Whole Program Optimization, MinSpace optimization, /Ob2
AnySuitable function inlining (to expose more code to elimination, this does
actually help here), /Zo (so that people can still debug it when lots of code
has been optimized out), turns of C++ RTTI (nobody is using it), /OPT:REF dead
code elimination, /OPT:ICF COMDAT folding, Link Time Code Generation, and
DebugFull debugging information creation.

/Gw global data optimization seemed to do nothing, which makes sense since
there isn't much going on in this project, very little in the way of actual
global data. Disabling C++ exceptions both in the project config (i.e. /EH-),
and disabling stdlib exceptions via _HAS_EXCEPTIONS=0, had no effect.
Strangely, with exceptions disabled and _HAS_EXCEPTIONS=0, exception functions
are still emitted in the binary (as seen in IDA). I presume it has something
to do with the fact that its a dll.

Enabling optimizations (even for Debug builds) should have no effect. The debug
builds were not actually using debugging featuers (not even assert), so nothing
should change.

pyshellext.dll   32 bit unimproved release size: 42KB
pyshellext.dll   32 bit   improved release size: 25KB
                                size reduction: -17KB
                             %  size reduction:   40%

pyshellext_d.dll 32 bit unimproved debug size:   85KB
pyshellext_d.dll 32 bit   improved debug size:   32KB
                               size reduction:  -53KB
                             %  size reduction:   62%


pyshellext.dll   64 bit unimproved release size: 52KB
pyshellext.dll   64 bit   improved release size: 30KB
                               size reduction:  -22KB
                             %  size reduction:   42%

pyshellext_d.dll 64 bit unimproved debug size:  105KB
pyshellext_d.dll 64 bit   improved debug size:   38KB
                               size reduction:  -67KB
                             %  size reduction:   63%

----------
components: Windows
messages: 365527
nosy: Alexander Riccio, paul.moore, steve.dower, tim.golden, zach.ware
priority: normal
severity: normal
status: open
title: Pyshellext room for binary size improvement
versions: Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue40145>
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