On 15.01.2021 01:13, Tom Lane wrote:
I borrowed my wife's Mac, which is still on Catalina and up to now
never had Xcode on it, and found some very interesting things.
Step 1: download/install Xcode 12.3, open it, agree to license,
wait for it to finish "installing components".
At this point, /Library/Developer/CommandLineTools doesn't exist,
and we have the following outputs from various probe commands:
% xcrun --show-sdk-path
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk
% xcrun --sdk macosx --show-sdk-path
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk
% xcodebuild -version -sdk macosx Path
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk
Also, cc -v reports
-isysroot
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk
Unsurprisingly, Xcode 12.3 itself only contains
% ls -l
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs
total 0
drwxr-xr-x 5 root wheel 160 Nov 30 07:27 DriverKit20.2.sdk
drwxr-xr-x 7 root wheel 224 Nov 30 07:27 MacOSX.sdk
lrwxr-xr-x 1 root wheel 10 Jan 14 15:57 MacOSX11.1.sdk -> MacOSX.sdk
Step 2: install command line tools (I used "xcode-select --install"
to fire this off, rather than the Xcode menu item).
Now I have
% ls -l /Library/Developer/CommandLineTools/SDKs
total 0
lrwxr-xr-x 1 root wheel 14 Jan 14 16:42 MacOSX.sdk -> MacOSX11.1.sdk
drwxr-xr-x 8 root wheel 256 Jul 9 2020 MacOSX10.15.sdk
drwxr-xr-x 7 root wheel 224 Nov 30 07:33 MacOSX11.1.sdk
which is pretty interesting in itself, because the same directory on
my recently-updated-to-Big-Sur Macs does NOT have the 11.1 SDK.
I wonder what determines which versions get installed here.
More interesting yet:
% xcrun --show-sdk-path
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk
% xcrun --sdk macosx --show-sdk-path
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk
% xcodebuild -version -sdk macosx Path
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk
and cc -v reports
-isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk
So apparently, "xcrun --show-sdk-path" (without any -sdk option)
is the most authoritative guide to the compiler's default sysroot.
However, googling turns up various people reporting that "xcrun
--show-sdk-path" returns an empty string for them, and our last
major investigation into this [1] found that there are some system
states where the compiler appears to have no default sysroot,
which I bet is the same thing. I do not at this point have a recipe
to reproduce such a state, but we'd be fools to imagine it's no
longer possible. My guess about it is that Apple's processes for
updating the default sysroot during system updates are just plain
buggy, with various corner cases that have ill-understood causes.
Also, after re-reading [1] I am not at all excited about trying to
remove the -isysroot switches from our *FLAGS. What I propose to do
is keep that, but improve our mechanism for choosing a default value
for PG_SYSROOT. It looks like first trying "xcrun --show-sdk-path",
and falling back to "xcodebuild -version -sdk macosx Path" if that
doesn't yield a valid path, is more likely to give a working build
than relying entirely on xcodebuild. Maybe there's a case for trying
"xcrun --sdk macosx --show-sdk-path" in between; in my tests that
seemed noticeably faster than invoking xcodebuild, and I've not yet
seen a case where it gave a different answer.
Thoughts?
regards, tom lane
[1] https://www.postgresql.org/message-id/flat/20840.1537850987%40sss.pgh.pa.us
Thanks for thorough investigation and sorry for the late reply.
I spent quite some time trying to understand / reverse engineer the
logic behind xcrun's default SDK selection. Apparently, "man xcrun" is
not accurate saying:
The SDK which will be searched defaults to the most recent
available...
I didn't find anything really useful or helpful.
"/Library/Developer/CommandLineTools" is hardcoded into
"libxcrun.dylib". On my machine xcrun scans
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs
and
/Library/Developer/CommandLineTools/SDKs
in that order, and loads "SDKSettings.plist" from each subdirectory. I
looked into plists, but couldn't find anything special about
"MacOSX10.15.sdk".
Okay, here is what I have:
% ls -l
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs
total 0
drwxr-xr-x 5 root wheel 160 Nov 30 15:27 DriverKit20.2.sdk
drwxr-xr-x 7 root wheel 224 Nov 30 15:27 MacOSX.sdk
lrwxr-xr-x 1 root wheel 10 Dec 17 14:25 MacOSX11.1.sdk -> MacOSX.sdk
% ls -l /Library/Developer/CommandLineTools/SDKs
total 0
lrwxr-xr-x 1 root wheel 14 Nov 17 02:21 MacOSX.sdk -> MacOSX11.0.sdk
drwxr-xr-x 8 root wheel 256 Nov 17 02:22 MacOSX10.15.sdk
drwxr-xr-x 7 root wheel 224 Oct 19 23:39 MacOSX11.0.sdk
% xcrun --show-sdk-path
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk
% xcrun --sdk macosx --show-sdk-path
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk
Oh, that's weird! Nevertheless I like you suggestion to call "xcrun"
from "configure".
Adding "--verbose" doesn't really explain anything, but just in case.
% xcrun --verbose --no-cache --find cc
xcrun: note: PATH =
'/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Library/Apple/usr/bin'
xcrun: note: SDKROOT =
'/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk'
xcrun: note: TOOLCHAINS = ''
xcrun: note: DEVELOPER_DIR = '/Applications/Xcode.app/Contents/Developer'
xcrun: note: XCODE_DEVELOPER_USR_PATH = ''
xcrun: note: xcrun_db =
'/var/folders/8x/jvqv7hyd5h98m7tz2zm9r0yc0000gn/T/xcrun_db'
xcrun: note: xcrun via cc (xcrun)
xcrun: note: database key is:
cc|/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk||/Applications/Xcode.app/Contents/Developer|
xcrun: note: looking up with
'/Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -sdk
macosx -find cc 2> /dev/null'
xcrun: note: lookup resolved with 'xcodebuild -find' to
'/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc
% xcrun --verbose --no-cache --sdk macosx --find cc
xcrun: note: looking up SDK with
'/Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -sdk
macosx -version Path'
xcrun: note: PATH =
'/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Library/Apple/usr/bin'
xcrun: note: SDKROOT = 'macosx'
xcrun: note: TOOLCHAINS = ''
xcrun: note: DEVELOPER_DIR = '/Applications/Xcode.app/Contents/Developer'
xcrun: note: XCODE_DEVELOPER_USR_PATH = ''
xcrun: note: xcrun_db =
'/var/folders/8x/jvqv7hyd5h98m7tz2zm9r0yc0000gn/T/xcrun_db'
xcrun: note: lookup resolved to:
'/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk'
xcrun: note: looking up SDK with
'/Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -sdk
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk
-version PlatformPath'
xcrun: note: PATH =
'/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Library/Apple/usr/bin'
xcrun: note: SDKROOT =
'/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk'
xcrun: note: TOOLCHAINS = ''
xcrun: note: DEVELOPER_DIR = '/Applications/Xcode.app/Contents/Developer'
xcrun: note: XCODE_DEVELOPER_USR_PATH = ''
xcrun: note: xcrun_db =
'/var/folders/8x/jvqv7hyd5h98m7tz2zm9r0yc0000gn/T/xcrun_db'
xcrun: note: lookup resolved to:
'/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform'
xcrun: note: PATH =
'/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Library/Apple/usr/bin'
xcrun: note: SDKROOT =
'/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk'
xcrun: note: TOOLCHAINS = ''
xcrun: note: DEVELOPER_DIR = '/Applications/Xcode.app/Contents/Developer'
xcrun: note: XCODE_DEVELOPER_USR_PATH = ''
xcrun: note: xcrun_db =
'/var/folders/8x/jvqv7hyd5h98m7tz2zm9r0yc0000gn/T/xcrun_db'
xcrun: note: xcrun via cc (xcrun)
xcrun: note: database key is:
cc|/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk||/Applications/Xcode.app/Contents/Developer|
xcrun: note: looking up with
'/Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -sdk
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk
-find cc 2> /dev/null'
xcrun: note: lookup resolved with 'xcodebuild -find' to
'/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc
