Link error with CompareObjectHandles

[jdm]

Using winapi::um::handleapi::CompareObjectHandles causes a link error to appear:

 = note: lld-link: error: undefined symbol: CompareObjectHandles
          >>> referenced by C:\git-mozilla\servo_ipc-channel\ipc-channel\src\platform\windows\mod.rs:349
          >>>               C:\git-mozilla\servo_ipc-channel\ipc-channel\target\debug\deps\ipc_channel-d21c39ad54b8c1b9.grgdvyw18xi6bb.rcgu.o:(_ZN82_$LT$ipc_channel..platform..windows..WinHandle$u20$as$u20$core..cmp..PartialEq$GT$2eq17h4f6b02f15a66ad57E)

I suspect this is because it's provided from kernelbase.lib instead of kernel32.lib, per https://docs.microsoft.com/en-us/windows/win32/api/handleapi/nf-handleapi-compareobjecthandles.

[angelortiz1007]

A potential fix has been identified.

According to Microsoft, the CompareObjectHandles () api is included in the WindowsApp.lib library. See:

https://docs.microsoft.com/en-us/uwp/win32-and-com/win32-apis

Based on this, I modified winapi-rs version 3's mod.rs file. I searched for handleapi feature and found that the library being used was kernel32. I changed it to WindowsApp" and my unresolved issue went away.

• ("handleapi", &["minwindef", "winnt"], &["kernel32"]),

• ("handleapi", &["minwindef", "winnt"], &["WindowsApp"]),

Note, there are many references to other APS using kernel32. These other APIs should be checked to see if the same change in their respective feature is required.

[retep998]

WindowsApp has a very significant effect on which dll a given symbol comes from and can affect the program's ability to run on older versions of windows. I'll have to verify what is actually affected before merging a PR for this.

[Xanewok]

Can we somehow conditionally compile the definition at https://docs.rs/winapi/0.3.7/src/winapi/um/handleapi.rs.html#23-26? Is there some mechanism already in the crate here to conditionally compile the newer parts of some previously-available interface?

[retep998]

@Xanewok Extern functions are not linked to unless used, so there is no need to have conditional compilation in winapi based on the targeted Windows version. If nothing uses CompareObjectHandles then no linker errors can occur involving it.

[angelortiz1007]

Don’t know if my reply will help on the background of CompareOjectHandles()… During running of the cargo tests an error was seen due to this API. CompareObjectHandls() is a Windows 10 specific API used to determine if the 2 passed in handles point to the same object. If it does, then the file handles are just clone of each other and the test passes. Unfortunately, this API is needed to accomplish this test. From: Peter Atashian <notifications@github.com> Sent: Wednesday, July 17, 2019 3:58 AM To: retep998/winapi-rs <winapi-rs@noreply.github.com> Cc: Angel Ortiz <aoble248@gmail.com>; Comment <comment@noreply.github.com> Subject: Re: [retep998/winapi-rs] Link error with CompareObjectHandles (#781) @Xanewok <https://github.com/Xanewok> Extern functions are not linked to unless used, so there is no need to have conditional compilation in winapi based on the targeted Windows version. If you don't use CompareObjectHandles then no linker errors can occur involving it. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#781?email_source=notifications&email_token=AMJITWHTP5PFY37NFR2KANLP73NIXA5CNFSM4H5GEKCKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD2DQXGQ#issuecomment-512166810> , or mute the thread <https://github.com/notifications/unsubscribe-auth/AMJITWHZXDZNIIB2S2J5NGLP73NIXANCNFSM4H5GEKCA> . <https://github.com/notifications/beacon/AMJITWFPXPL5ZEKOY25CHI3P73NIXA5CNFSM4H5GEKCKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD2DQXGQ.gif>