Add a note about OpenSSL for macOS developers.

[z-aki]

Describe the bug
Since the "build after push" workflow uses this hack, it makes sense to add something that works for macOS users to the build docs.
echo "PKG_CONFIG_PATH=$(brew --prefix)/opt/[email protected]/lib/pkgconfig" >> $GITHUB_ENV

I saw that pkg_check_modules is being used for finding grpc. If CMake's modules were used, I could specify OPENSSL_ROOT_DIR and make it work.

To Reproduce
Run
cmake -DENABLE_UNIT_TESTS=OFF -DENABLE_FUNC_TESTS=OFF ../Bear/
And see

-- Looking for gRPC::grpc++ dependency
-- Checking for modules 'protobuf>=3.11;grpc++>=1.28'
--   Package 'openssl', required by 'grpc', not found
-- Looking for gRPC::grpc++ dependency -- not found

Expected behavior
Find the keg only OpenSSL using some environment variable or cmake variable.

Environment:

• OS name: Darwin
• OS version: 10.14
• OS architecture: x86_64
• Bear version: master branch
• Bear install method: building from source

[z-aki]

Now that I overcame this hurdle, and the one listed here #313, I was greeted with std::filesystem::path not available on macOS 10.14. I tried to avoid that by using gcc-10 and g++-10 as compliers. They were set properly for top level project:

cmake -C ../xccmake.cmake -DENABLE_UNIT_TESTS=OFF -DENABLE_FUNC_TESTS=OFF ../Bear/
loading initial cache file ../xccmake.cmake
-- The C compiler identification is GNU 10.2.0
-- The CXX compiler identification is GNU 10.2.0

but sub-projects are a mess:

[ 55%] Performing configure step for 'BearSource'
loading initial cache file /Users/e/Applications/Bear/build/subprojects/tmp/BearSource/BearSource-cache-Release.cmake
-- The C compiler identification is AppleClang 10.0.1.10010046
-- The CXX compiler identification is GNU 10.2.0

Creating the main project as an external project seems highly fragile to me.
Moving on with this mismatched set of compilers was set to be doomed from the start, but here are the linker errors:

linker error

[  0%] Built target grpc_dependency
[  0%] Built target googletest_dependency
[  0%] Built target nlohmann_json_dependency
[  0%] Built target fmt_dependency
[  0%] Built target spdlog_dependency
[ 11%] Performing build step for 'BearSource'
[  1%] Built target flags_a
[  3%] Built target shell_a
[ 15%] Built target sys_a
[ 30%] Built target exec_a
[ 35%] Built target supervise_a
[ 39%] Built target reporter_a
[ 41%] Building CXX object intercept/CMakeFiles/er.dir/source/report/supervisor/Application.cc.o
[ 43%] Building CXX object intercept/CMakeFiles/er.dir/source/report/supervisor/main.cc.o
[ 45%] Linking CXX executable er
Undefined symbols for architecture x86_64:
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      ...
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      ...
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status
make[5]: *** [intercept/er] Error 1
make[4]: *** [intercept/CMakeFiles/er.dir/all] Error 2
make[3]: *** [all] Error 2
make[2]: *** [subprojects/Stamp/BearSource/BearSource-build] Error 2
make[1]: *** [CMakeFiles/BearSource.dir/all] Error 2
make: *** [all] Error 2

[z-aki]

All this because Bear 4.0 is not available on brew.

[rizsotto]

Hey @z-aki , thanks for this report.

Yeah, the sub-project might still have bugs, but it's still the best way to handle 3rd-party-dependencies (to my best knowledge and according to the book i've read on the subject)... I was only deal with the CXX compiler, because there are no C source files in the project. But that might be still used in cases when the C linking is explicitly requested. I'll update that part.

About using CMake files or PkgConfig to find gRPC: not all distro install the CMake files, but all install the PkgConfig files. (eg.: Fedora has only PkgConfig files in the package.) I'm happy to get a PR where it looks for the CMake file first and falls back to PkgConfig. :)

Yes, brew does not yet have the latest Bear. (My experience with brew got painful, specially the gRPC dependency gets broken every 3 months. I think it's still in a broken state now.) I'm happy to get PRs for this platform, since I do not own macOS machine.

[z-aki]

I have zero experience with GCC. I can probably make it work with Apple clang and LLVM clang if the std::filesystem::path restriction is removed.

[rizsotto]

Why shall the std::filesystem be removed? According to this page, those shall be available on macOS too with the Clang compiler.

[z-aki]

• https://stackoverflow.com/questions/56924853/why-xcode-11-beta-cant-use-c17s-filesystem-header
• https://stackoverflow.com/questions/58648316/does-llvm-9-support-stdfilesystem-on-versions-of-the-mac-prior-to-10-15?noredirect=1&lq=1

I just found these threads, so I'll try experimental:

• https://stackoverflow.com/questions/49577343/filesystem-with-c17-doesnt-work-on-my-mac-os-x-high-sierra
• building tutorials cannot work on Mac OS Catalina 10.15 DeadSix27/waifu2x-converter-cpp#204

[z-aki]

To clarify, std::filesystem is fine, std::filesystem::path is not. GCC works fine however. But on default installations, GCC is just an alias to Clang. I made some changes to use proper GCC via brew but Bear shouldn't be supporting some compiler installed using some package manager.(EDIT LLVMClang is an exception to that. That and AppleClang behave very similar.)

[z-aki]

Since AppleClang introduced <filesystem> in Xcode 11, people using less than that will have to download llvm toolchain from either brew or compile from source. (I've done the latter.) So my changes will target those people.

LLVMClang compiles and runs code with std::filesystem::path just by adding add_compile_definitions(_LIBCPP_DISABLE_AVAILABILITY). So one problem down.

[z-aki]

Yeah, the sub-project might still have bugs, but it's still the best way to handle 3rd-party-dependencies (to my best knowledge and according to the book i've read on the subject)

Yes, but only for third party projects. For the main project (Bear), I'm having a difficult time adding (experimenting with -stdlib=libc++) /removing (labsl_dynamic_annotations) linker flags, adding definitions _LIBCPP_DISABLE_AVAILABILITY , using generators other than make or ninja since the ExternalProject_Add does the last part opaquely in some sub-directory.

I hope it would be welcome if we trade-off the ease of a single ExternalProject_Add call with a more flexible and configurable Cmake script.

[rizsotto]

I'm not sure if the external project is the biggest enemy in this build. :)

What is the pain point to add/remove flags in an external project?

[z-aki]

What is the pain point to add/remove flags in an external project?

I didn't realise that I had to add flags, definitions in the source/CMakeLists.txt file, not the top level one.

I'm not sure if the external project is the biggest enemy in this build. :)

• I like to work with Xcode generator and external project configures BearProject in some folder down there not quickly available to me. So in the Xcode project all I see is Cmake files.
• Since that configuration happens as an Xcode build step, I cannot set environment variables easily.

In the ideal world, Cmake configures once, and then we get straight to the C++ code.

[z-aki]

https://pasteall.org/b1O2/slim This is what got me over all the linking errors. Though I admit I had to issue a brew switch abseil 20200225.2 to avoid the -labsl_dynamic_annotations issue. Now when I launch bear from its custom install directory, it says

$ ../install/bin/bear --
/bin/sh: /bin/intercept: No such file or directory
/bin/sh: /bin/citnames: No such file or directory
$

Do you happen to know why ?

[rizsotto]

add_dependencies(
    bear

There you need to list all targets (not only bear, but intercept, wrapper and citnames too).

And also look for the source/config.h.in that contains the path where these binaries will be installed. (In your case it's /bin, but it's suppose to be /usr/local/bin, unless specified otherwise).

[rizsotto]

@z-aki what is the trick to downgrade the abseil dependency? Can you pass what command to run for that? (I would like to see the build passing on CI again.)

[rizsotto]

About the external project... I'm not using XCode, but CLion. And instead of opening the project CMakeList.txt I open the source/CMakeList.txt as a project, and it works like a charm. :)

If you can't have all dependencies from packages, but the parent project has to build it, then you need to pass a few flags in the settings.

I am not saying this is ideal, but might help to work with the current CMake setup.

[z-aki]

brew switch abseil 20200225.2

If that doesn't work right away, download the abseil tarball from an old brew formula (ruby file of abseil) and put it in Cellar/abseil/ and run the switch again.

I think better fix would be to remove the link flag using Cmake if that library is now merged in some other flag.

I decided to drop the idea of removing subproject for Bear reluctantly. It's a bigger change, connected with tests and stuff. Here's a probable filesystem fix: https://pasteall.org/UHVa/slim I'll open a PR once I test a few things.

[z-aki]

About the external project... I'm not using XCode, but CLion. And instead of opening the project CMakeList.txt I open the source/CMakeList.txt as a project, and it works like a charm. :)

Hmm, didn't think of that. Thanks. Changing the source dir is better. I get some false positives by clangd about missing headers, but it's better than nothing.

CC=clang CXX=clang++ cmake ../Bear/source/ -DCMAKE_INSTALL_PREFIX=/Users/t/Applications/Bear/install \
-DROOT_INSTALL_PREFIX=/Users/t/Applications/Bear/install -DCMAKE_CXX_STANDARD=17 \
-DCMAKE_PROJECT_VERSION=3.0.3 -G "Sublime Text 2 - Ninja" -DCMAKE_EXPORT_COMPILE_COMMANDS=ON

Anyway, pull request here: #334

[rizsotto]

Thanks @z-aki for your time and efforts. I did the rewrite (of Bear) mostly to satisfy macOS users. (The concept of using compiler wrappers were to address the macOS static make command problem and workaround SIP limitations.)

To my best understanding the current problems with this platform are:

• That Brew grpc package is broken (which I've run into on the CI). Solution for this can be just waiting while it got fixed. :)
  • I've tried to lean into it, but it's hard to know what needs to be done.
• And std::filesystem::path is not available on older versions. Solutions for this can be...
  • Not use std::filesystem::path type. Which way I have to implement if for all platforms.
  • Use newer compilers which have support. (This is what you've done. I think it specific to certain versions of macOS, and the workaround should be in the packaging repo.)