Conan on Mac can't recognize compiler correctly

[zamazan4ik]

Hello, https://travis-ci.org/procxx/kepka/jobs/322618396

on the link you can see that Conan recognize compiler as gcc 4.2 on Travis, but it's not true.

[memsharded]

I think it might be because conan detects the compiler version executing: gcc --version, and in your case it might be that only g++ is configured as the default one. Can you output in your script the output of gcc --version, or better, configure gcc 8.1 as the default gcc too?

[berkus]

@memsharded on osx, gcc and g++ are system aliases for clang.

[memsharded]

To further clarify why not g++ is used in the detection, the rationale is that there are many projects that contain a mixture of C and C++, so both compilers are used. Sometimes in different libraries, but sometimes also in the same library or package. As it seems quite important to maintain consistency, there is single settings.compiler=gcc setting (not g++), and a single settings.compiler.version value in the default settings.

[berkus]

I tried passing -s compiler.version=7.2 to force detection override, subsequently cmake fails because conan generates invalid compiler identification:

-- Current conanbuildinfo.cmake directory: /Users/travis/build/procxx/kepka/_build_
CMake Error at _build_/conanbuildinfo.cmake:474 (message):
  Incorrect 'gcc', is not the one detected by CMake: 'AppleClang'
Call Stack (most recent call first):
  _build_/conanbuildinfo.cmake:173 (conan_check_compiler)
  CMakeLists.txt:30 (conan_basic_setup)

[memsharded]

Ok, I think I get the issue. This code is in detect.py:

cc = os.environ.get("CC", "")
cxx = os.environ.get("CXX", "")
if cc or cxx:  # Env defined, use them
        output.info("CC and CXX: %s, %s " % (cc or "None", cxx or "None"))
        command = cc or cxx
        if "clang" in command.lower():
              return _clang_compiler(output, command)

Setting the CXX env var to "clang++" instead of "g++" might workaround the issue, while better detection is developed.

[memsharded]

If you are overriding in command line, you have also to override the compiler, that is not gcc:

$ conan install . -s compiler=apple-clang -s compiler.version=7.3 -s ...

Beware 7.2 is not a default compiler.version for apple-clang. You can check the default settings values in settings.yml file.

[berkus]

So I reckon there's no portable way to set this up... ok, i will use different per-platform invocations then.

[memsharded]

I am defining this as an improvement, lets aim to do this for 1.1, but also low priority, if 1.1 is packed, it might be delayed. Thanks very much for the feedback!

[pvicente]

Hi @ZaMaZaN4iK ,

We've been investigating the issue and it was happening in conan 0.30.3 see https://travis-ci.org/procxx/kepka/jobs/322618395#L1364. I've tried to reproduce the issue with latest conan version 1.0.4 https://travis-ci.org/pvicente/kepka/jobs/342041385#L1959 but the behaviour detecting the compiler is ok.

Now it looks like you have another problem but not related with conan,

-- Performing Test WNCE_FLAG_SUPPORTED - Success
-- Found framework /System/Library/Frameworks/Cocoa.framework
-- Found framework /System/Library/Frameworks/CoreFoundation.framework
-- Found framework /System/Library/Frameworks/CoreServices.framework
-- Found framework /System/Library/Frameworks/ApplicationServices.framework
-- Found framework /System/Library/Frameworks/CoreText.framework
-- Found framework /System/Library/Frameworks/CoreGraphics.framework
-- Found framework /System/Library/Frameworks/Foundation.framework
-- Found framework /System/Library/Frameworks/OpenGL.framework
-- Found framework /System/Library/Frameworks/QuartzCore.framework
-- Found framework /System/Library/Frameworks/AGL.framework
-- Found framework /System/Library/Frameworks/Security.framework
-- Found framework /System/Library/Frameworks/SystemConfiguration.framework
-- Found framework /System/Library/Frameworks/Carbon.framework
-- Found framework /System/Library/Frameworks/CoreAudio.framework
-- Found framework /System/Library/Frameworks/AudioToolbox.framework
-- Found framework /System/Library/Frameworks/AudioUnit.framework
-- Found framework /System/Library/Frameworks/AppKit.framework
-- Found framework /System/Library/Frameworks/CoreWLAN.framework
-- Found framework /System/Library/Frameworks/IOKit.framework
-- C CXX target Telegram cotired without unity build excluding 18 files.
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/travis/build/pvicente/kepka/_build_
+cmake --build . -- -v
ninja: error: '/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk/System/Library/Frameworks/AudioToolbox.framework', needed by 'bin/Telegram.app/Contents/MacOS/Telegram', missing and no known rule to make it
+exit 1

If you don't mind I'm going to close the issue but feel free to reopen it if you can see any problem with conan.

Cheers, Pedro

[pvicente]

Sorry @ZaMaZaN4iK ,

I've reproduced the same error with the latest version of conan 1.0.4.

https://travis-ci.org/pvicente/kepka/jobs/342447099

Working on a proper fix to make it more "portable".

[memsharded]

I have been asking and investigating:

@berkus

on osx, gcc and g++ are system aliases for clang.

That is not totally accurate. The OSX gcc/g++ are actually gnu gcc frontends using the apple-clang llvm backend. https://stackoverflow.com/questions/19535422/os-x-10-9-gcc-links-to-clang

There is some ongoing work in https://github.com/conan-io/conan/pull/2487.

But I think the logic should probably be: Skip the gcc (as clang frontend) in OSX in the default conan detection of compiler. So in OSX, conan will be able to detect normal "apple-clang" clang compiler, and maybe "gcc", but as complete gcc, not that clang frontend.

[berkus]

JFYI: The "GCC" that came with 10.8 was really GCC front-end with LLVM back-end.

Starting from 10.9, gcc is just an alias running clang, gcc has been dropped completely by Apple.