Invalid check for availability of futimens function for macOS platform

[lolgear]

Reproduction steps

Open src/unix/posix.h

Expected behavior

Everything works fine.

Actual behavior

Xcode warning: futimens is only available for macOS 10.13 or newer.
I build it for a project with minimum deployment target 10.10.

Version of libgit2 (release number or SHA1)

Latest master.

Operating system(s) tested

macOS 10.16
Xcode 12.5

[ethomson]

What version of cmake? It claims to honor the deployment target version for futimens

[lolgear]

I use Cmake 3.20.2 (Installed from Homebrew)
I run

#!/bin/sh

export MACOSX_DEPLOYMENT_TARGET=10.10

rm -rf "xcode"
mkdir "xcode"
cd "xcode"
cmake -G "Xcode" ..
open "libgit2.xcodeproj"

Open Xcode 12.5 and build git2 target.
Xcode complains about futimens.
Maybe project settings are wrong in Xcode.

[lolgear]

Could you confirm that my test by Xcode project is relevant?

[tiennou]

I can confirm that something is fishy, here's the output from a run of libgit2/objective-git, that builds with SDKROOT\=/Applications/Xcode-12.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk and MACOSX_DEPLOYMENT_TARGET\=10.10.

[lolgear]

I posted a question about this issue at CMake forums.

And at one moment I figured out that I do something wrong.
I compared generated .c file and a file that is proposed in a CMake futimens issue.

They are different. Generated file doesn't include headers to search for.
It defines a function futimens.

I suggested to use check_symbol_exists with a provided header sys/stat.h.

enable_warnings(error)
check_symbol_exists(futimens sys/stat.h HAVE_FUTIMENS)
# check_function_exists(futimens HAVE_FUTIMENS)
IF (HAVE_FUTIMENS)
	SET(GIT_USE_FUTIMENS 1)
ENDIF()
#message(FATAL_ERROR)

[lolgear]

@ethomson
They changed something in recent release ( cmake 2.23.1 - 2.23.2 ) and our setup doesn't work.
MACOSX_DEPLOYMENT_TARGET doesn't affect futimens availability anymore.

/// Always find futimens regardless deployment target variable value.
MACOSX_DEPLOYMENT_TARGET=10.10 cmake -S "$SCRIPT_DIRECTORY" -B "$SCRIPT_DIRECTORY/xcode" -G "Xcode"