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Author eryksun
Recipients GeekyShacklebolt, eryksun, paul.moore, steve.dower, tim.golden, vstinner, zach.ware
Date 2019-02-02.18:05:49
SpamBayes Score -1.0
Marked as misclassified Yes
Message-id <1549130749.25.0.475719799788.issue32560@roundup.psfhosted.org>
In-reply-to
Content 
It should be fine. If the docs don't require initializing cb, we can assume it's done for us. 

For example, msvcrt.dll calls GetStartupInfo without initializing this field:

    0:000> kc 3
    Call Site
    KERNELBASE!GetStartupInfoW
    msvcrt!ioinit
    msvcrt!__CRTDLL_INIT

In x64, the first argument (lpStartupInfo) is in rcx. We see the DWORD (dd) value of cb is initially 0:

    0:000> dd @rcx l1
    00000094`25ddefd0  00000000

Continue to the ret[urn] instruction via pt and check that the returned value of cb is sizeof(*lpStartupInfo):

    0:000> pt
    KERNELBASE!GetStartupInfoW+0xb2:
    00007fff`8ae41282 c3              ret
    0:000> dd 94`25ddefd0 l1
    00000094`25ddefd0  00000068
History
Date User Action Args
2019-02-02 18:05:50eryksunsetrecipients: + eryksun, paul.moore, vstinner, tim.golden, zach.ware, steve.dower, GeekyShacklebolt
2019-02-02 18:05:49eryksunsetmessageid: <1549130749.25.0.475719799788.issue32560@roundup.psfhosted.org>
2019-02-02 18:05:49eryksunlinkissue32560 messages
2019-02-02 18:05:49eryksuncreate