stream: Fix MacOS build. fsync as alias for fdatasync.

[devnexen]

No description provided.

[nikic]

I'm confused about why this works in CI (using macos 10.15). Was this function recently added/removed?

[devnexen]

I spotted it because of implicit declaration... warning and indeed macos does not have it.

[nikic]

That just leaves me more confused. We build with -Werror in CI, and I also checked that the test case for fdatasync is running and passing. The build seems to be picking up the symbol from somewhere...

[devnexen]

There is a syscall id mentioning it but not wrapper function, no man page entry for it.
And seems before it was not neither gbrault/picoc#145 (comment)

[devnexen]

That just leaves me more confused. We build with -Werror in CI, and I also checked that the test case for fdatasync is running and passing. The build seems to be picking up the symbol from somewhere...

Does it imply -Werror-implicit-function-declaration (or should be added to CI) ?

[nikic]

I just double checked this, and this the the used compilation command:

/bin/sh /Users/runner/work/1/s/libtool --silent --preserve-dup-deps --mode=compile cc -Imain/streams/ -I/Users/runner/work/1/s/main/streams/ -I/Users/runner/work/1/s/include -I/Users/runner/work/1/s/main -I/Users/runner/work/1/s -I/Users/runner/work/1/s/ext/date/lib -I/usr/local/Cellar/libxml2/2.9.10_2/include/libxml2 -I/usr/local/Cellar/krb5/1.19.1/include -I/usr/local/Cellar/[email protected]/1.1.1k/include -I/usr/local/Cellar/zlib/1.2.11/include -I/usr/local/opt/bzip2/include -I/usr/local/Cellar/libffi/3.3_3/include -I/usr/local/Cellar/libpng/1.6.37/include/libpng16 -I/usr/local/Cellar/webp/1.2.0/include -I/usr/local/Cellar/jpeg/9d/include -I/usr/local/opt/freetype/include/freetype2 -I/usr/local/opt/gettext/include -I/usr/local/opt/gmp/include -I/usr/local/opt/libiconv/include -I/usr/local/Cellar/icu4c/68.2/include -I/usr/local/Cellar/oniguruma/6.9.6/include -I/Users/runner/work/1/s/ext/mbstring/libmbfl -I/Users/runner/work/1/s/ext/mbstring/libmbfl/mbfl -I/usr/local/opt/libpq/include -I/usr/local/opt/aspell/include/pspell -I/usr/local/opt/readline/include -I/usr/local/Cellar/libsodium/1.0.18_1/include -I/usr/local/opt/tidyp/include/tidyp -I/usr/local/Cellar/libxslt/1.1.34_2/include -I/usr/local/Cellar/libzip/1.7.3/include -I/Users/runner/work/1/s/TSRM -I/Users/runner/work/1/s/Zend -fno-common -Wall -Wextra -Wno-strict-aliasing -Wno-unused-parameter -Wno-sign-compare -g -fvisibility=hidden -O0 -DZEND_SIGNALS -Werror -DZEND_ENABLE_STATIC_TSRMLS_CACHE=1 -c /Users/runner/work/1/s/main/streams/plain_wrapper.c -o main/streams/plain_wrapper.lo -MMD -MF main/streams/plain_wrapper.dep -MT main/streams/plain_wrapper.lo

It includes -Wall -Wextra -Werror, so should definitely catch implicit function declarations.

My best guess is that we're pulling in a header somewhere that has an fdatasync compatibility define...

[devnexen]

Then yes it is the only reason it could happen I locally does not use so many dependencies.

[nikic]

I've dumped the preprocessed code (-E) for the file: https://dev.azure.com/phpazuredevops/eb1f6f74-bc61-47a6-a414-0e3ff41c9bb4/_apis/build/builds/16109/logs/28

fdatasync() is being called directly and there is no declaration for it, so it's not the case that it was defined by some other header. But for some reason the build does not fail. I even added an explicit -Werror=implicit-function-declaration, but that also had no effect.

[devnexen]

I have a slighty better idea what is happening now. I did a quick sample local code and if I compile with clang from Xcode then it is fine fdatasync symbol is picked up rightfully (but fdatasync not present in the headers tough), however with gcc/clang compilers from homebrew then I get the warning. Maybe the best course of action would be configure time detection then what do you think ?

[nikic]

I have a slighty better idea what is happening now. I did a quick sample local code and if I compile with clang from Xcode then it is fine fdatasync symbol is picked up rightfully (but fdatasync not present in the headers tough), however with gcc/clang compilers from homebrew then I get the warning.

Any idea where Xcode is getting the symbol from?

Maybe the best course of action would be configure time detection then what do you think ?

Yes, I think this would make the most sense. After all, macos may also not be the only system without this function. We can add it to the list in

php-src/configure.ac

Line 545 in d24cf1a

AC_CHECK_FUNCS(

[devnexen]

No idea, it seems part of Apple's secret sauce :)

[morrisonlevi]

fdatasync doesn't exist in /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain on Mac OS 10.15. There is a function which is not defined in a header: https://github.com/apple/darwin-xnu/blob/d4061fb0260b3ed486147341b72468f836ed6c8f/bsd/vfs/vfs_syscalls.c#L7708.

I have no idea why. My guess... don't use it?

[trowski]

I'm still seeing php-src/main/streams/plain_wrapper.c:559:11: warning: implicit declaration of function 'fdatasync' is invalid in C99 when compiling with clang on macOS. Is there a path or something else I need to be setting, or is there still an issue with fdatasync on macOS?