Unused letters in Windows-specific pragma optimize

[gvanrossum]

BPO	43166
Nosy	@gvanrossum, @pfmoore, @db3l, @vstinner, @tjguk, @zware, @zooba, @neonene
PRs	bpo-43166 Disable ceval.c optimisations for Windows debug builds #24485 bpo-43166: Disable ceval.c optimizations for Windows debug builds again #32023

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/zooba'
closed_at = <Date 2021-02-09.18:13:51.078>
created_at = <Date 2021-02-08.19:48:37.646>
labels = ['3.10', 'OS-windows']
title = 'Unused letters in Windows-specific pragma optimize'
updated_at = <Date 2022-03-23.00:35:32.177>
user = 'https://github.com/gvanrossum'

bugs.python.org fields:

activity = <Date 2022-03-23.00:35:32.177>
actor = 'steve.dower'
assignee = 'steve.dower'
closed = True
closed_date = <Date 2021-02-09.18:13:51.078>
closer = 'steve.dower'
components = ['Windows']
creation = <Date 2021-02-08.19:48:37.646>
creator = 'gvanrossum'
dependencies = []
files = []
hgrepos = []
issue_num = 43166
keywords = ['patch']
message_count = 4.0
messages = ['386646', '386735', '387349', '415843']
nosy_count = 8.0
nosy_names = ['gvanrossum', 'paul.moore', 'db3l', 'vstinner', 'tim.golden', 'zach.ware', 'steve.dower', 'neonene']
pr_nums = ['24485', '32023']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue43166'
versions = ['Python 3.10']

[gvanrossum]

A coworker happened to look at our use of #pragma optimize() for Windows (VS 2017) and noticed:

unless there’s something I’m missing, the ‘a’ and ‘w’ portions of the string being passed to the optimize pragma are not doing anything; I’m pretty sure they’ve been useless for 10+ years. The ‘g’ means turn on global optimizations and the ‘t’ means optimize for “time” (i.e. speed). See the documentation at https://docs.microsoft.com/en-us/cpp/preprocessor/optimize?view=msvc-160

[zooba]

New changeset b74396c by Steve Dower in branch 'master':
bpo-43166: Disable ceval.c optimisations for Windows debug builds (GH-24485)
b74396c

[vstinner]

Since this change, AMD64 Windows10 3.x buildbot started to crash with Windows fatal exception: stack overflow -> see bpo-43271.

[zooba]

New changeset cd05d0a by neonene in branch 'main':
bpo-43166: Disable ceval.c optimizations for Windows debug builds (GH-32023)
cd05d0a