Use C99 Variable Length Arrays when possible

[AZero13]

Feature or enhancement

Proposal:

Not all cases can be converted because some structs with this are members in the middle of bigger structs, so changing them introduces warnings. Leave them alone for now.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-144048: Use flexible array members #144049

[picnixz]

This is code churn IMO and not worth addressing.

[picnixz]

cc @markshannon @vstinner

[serhiy-storchaka]

This produces a compiler warning C4200 on Windows.

Warning:     35>D:\a\cpython\cpython\Include\cpython\pystate.h(61,16): warning C4200: nonstandard extension used: zero-sized array in struct/union [D:\a\cpython\cpython\PCbuild\_wmi.vcxproj]
         (compiling source file '../PC/_wmimodule.cpp')
             D:\a\cpython\cpython\Include\cpython\pystate.h(61,16):
             This member will be ignored by a defaulted constructor or copy/move assignment operator

[vstinner]

Recently, I modified tracemalloc to use flexible array: commit 83d8134 of issue gh-127635. The issue was a report from GCC/Clang syntax checker for the flexible array usages.