[cfe-dev] Errors in local system headers when using clang libTooling tool

[Eberhard Gräther via cfe-dev]

Hello cfe-dev,

I’m using clang libTooling for creating a GUI developer tool, currently with clang 6.0. The tool makes use of the local system headers when analyzing source code. From my local compiler I get these system header paths:

    $ clang++ -x c++ -v -E /dev/null
    ...
    #include <...> search starts here:
     /usr/local/include
     /opt/local/include
     /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1
     /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/9.1.0/include
     /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include
     /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk/usr/include
     /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk/System/Library/Frameworks (framework directory)
    …


My local toolchain is based on Xcode:

    $ clang++ -v
    clang version 5.0.1 (http://llvm.org/git/clang.git 232230afd349ceeb784720d2266e2288523d871f) (http://llvm.org/git/llvm.git cbc2c76b286c38a1fd006543b6b224c06cd96df1)
    Target: x86_64-apple-darwin17.5.0
    Thread model: posix
    InstalledDir: /usr/local/bin


My tool usually works fine, and most source code can be analysed without problems. But sometimes there are errors like this one:

    /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/9.1.0/include/emmintrin.h:2261:19: fatal error: use of undeclared identifier '__builtin_ia32_pavgb128'
      return (__m128i)__builtin_ia32_pavgb128((__v16qi)__a, (__v16qi)__b);
                      ^
    error: use of undeclared identifier ‘__builtin_ia32_pavgb128'


I found out that this problem might be related to the preprocessor definitions of my tool. My tool either uses the wrong ones or misses some. I can get a list from my local compiler and make my tool use them:

    $ clang++ -x c++ -E -dM /dev/null
    #define OBJC_NEW_PROPERTIES 1
    #define _LP64 1
    #define __APPLE_CC__ 6000
    #define __APPLE__ 1
    #define __ATOMIC_ACQUIRE 2
    #define __ATOMIC_ACQ_REL 4
    #define __ATOMIC_CONSUME 1
    #define __ATOMIC_RELAXED 0
    #define __ATOMIC_RELEASE 3
    …


But that just switches the problem to some other location:

    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk/usr/include/stdlib.h:162:54: fatal error: redefinition of parameter 'restrict'
    size_t   mbstowcs(wchar_t * __restrict , const char * __restrict, size_t);
                                                          ^
    /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk/usr/include/sys/cdefs.h:209:20: note: expanded from macro '__restrict'
    #define __restrict      restrict
                            ^
    error: redefinition of parameter ‘restrict’


I couldn’t find a good resource explaining me this situation yet. What am I doing wrong here?
Is this a problem of wrong/missing preprocessor definitions?
Or does my clang 6.0 tool not match with my local clang 5.0.1 toolchain’s system headers?
Do I need to ship certain system headers with my tool?

Thank you,
Eberhard Gräther


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