Environment.OSVersion returns wrong info on Big Sur

[wfurt]

This returns 10.16 and may be caveat of the beta.
However, is is curious that OS tools report 11.0 as expected:

furt@macos-11 foo % sysctl kern.osproductversion
kern.osproductversion: 11.0

furt@macos-11 foo % sw_vers
ProductName:	macOS
ProductVersion:	11.0
BuildVersion:	20A5343i

This seems to also impact dotnet --info and perhaps package selection.

cc: @akoeplinger @marek-safar @danmosemsft

[Dotnet-GitSync-Bot]

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[danmoseley]

runtime/src/libraries/Common/src/Interop/OSX/Interop.libobjc.cs

Lines 34 to 50 in c87e75e

	internal static Version GetOperatingSystemVersion()
	{
	int major = 0;
	int minor = 0;
	int patch = 0;
	IntPtr processInfo = objc_msgSend(objc_getClass("NSProcessInfo"), sel_getUid("processInfo"));
	if (processInfo != IntPtr.Zero)
	{
	NSOperatingSystemVersion osVersion = get_operatingSystemVersion(processInfo, sel_getUid("operatingSystemVersion"));
	checked
	{
	major = (int)osVersion.majorVersion;
	minor = (int)osVersion.minorVersion;
	patch = (int)osVersion.patchVersion;

[wfurt]

yah, I saw that. Some objective C messaging...

[danmoseley]

This suggests everything ultimately reads /System/Library/CoreServices/SystemVersion.plist - maybe not in any more. What is in there on your system?

[wfurt]

<plist version="1.0">
<dict>
        <key>ProductBuildVersion</key>
        <string>20A5343i</string>
        <key>ProductCopyright</key>
        <string>1983-2020 Apple Inc.</string>
        <key>ProductName</key>
        <string>macOS</string>
        <key>ProductUserVisibleVersion</key>
        <string>11.0</string>
        <key>ProductVersion</key>
        <string>11.0</string>
        <key>iOSSupportVersion</key>
        <string>14.0</string>
</dict>
</plist>

Parsing files seems tricky. What is curious is that we seems to be using API Apple does not use for system utilities.
They may fix it eventually. If supported on mobile devices, systctl seems easies. We already have wrapper and it gives back string.

[vcsjones]

It's dependent on which macOS SDK is used. If the code is built with xcode 12 beta and uses the macOS 11 SDK, then operatingSystemVersion returns 11. If you build using the macOS 10.15 SDK or lower, it returns a "compat" version of 10.16.

I think Apple did this to mitigate older apps making the assumption that major version would be 10 forever, and only return the later version on the new SDK.

[wfurt]

Interesting. Since we do single build on 10.13, we may do some fix-ups here.

[wfurt]

This is more tricky than I expected. I added code to get version via sysctl. However it seems to also go through compat layer so when I ask for kern.osproductversion from command line, I get 11.0 but when I ask for the same value from dotnet I get 10.16. Also there is environment variable SYSTEM_VERSION_COMPAT and when I set it to 0, I get 11.0 using existing dotnet builds.

I think we have following options IMHO:

1. update SDK on build machines
2. add mapping 10.16 -> 11.0
3. set SYSTEM_VERSION_COMPAT to 0 if not set already somewhere.
4. use different method - like parsing files - to detect version

While 1. is probably best option long term, 2. would allow us to move forward quickly and safely. We can itterate on the fix once 11.0 really ships and is stable. I personally don't like fourth option. That seems something hard to maintain over time.

Let me know @danmosemsft what do you want to do.

There is some (unofficial) article suggesting this may be permanent:
https://eclecticlight.co/2020/07/06/why-big-sur-wont-stumble-over-version-numbers/

[jkotas]

2. would allow us to move forward quickly and safely

+1

[danmoseley]

I like # 2 ... and eventually we will build 6.0 (?) using the 11.0 SDK and we can remove it. I assume we will backport this also, but it woudl be for Oct at this point which is fine.

[wfurt]

ok. SYSTEM_VERSION_COMPAT can be used as workaround by anybody who really want to see 11.0 right now. (and we added compat 10.16 RID as well)